Eve's been around for a while, but I've been doing something else (i.e. playing World of Warcraft) so I didn't try it. I generally prefer "science fiction" flavored stuff over fantasy, but MMOs are in large part about sunken cost.
Eve Online is essentially multiplayer Elite (or, if you're a Mac gamer, multiplayer Escape Velocity in 3D; if you're under 30 it's multiplayer Privateer), only with the fun part (dogfighting) removed and the other fun part (trading in slaves and illegal drugs) replaced with something resembling E-Trade. Actually, E-Trade is a lot more fun (and more realistic!).
I won't bother criticizing the back story (apparently some people are just genetically predisposed to liberal democracy -- quick, better call Condi, I think this whole Iraq thing might be a mistake) because EverQuest and World of Warcraft prove that a back story can be an uninspired kitchen sink of stolen cliches and the game can still be great. I will say that Eve Online's back story is essentially fantasy (i.e. the past was great the present sucks) and not science fiction, and that it aspires to be a uninspired kitchen sink of stolen cliches.
When you start the game (about 1h after installing it and waiting for it to patch) you have two sets of choices to make; one is your character's appearance, which can be customized by a pretty amazing set of options (e.g. you can narrow your gaze by increments, give your character a smile, snarl, or twisted leer), and some other stuff (e.g. professional background) that is -- I'm told* -- very important but for which you have no useful information. So basically, think of this as 200 questions of no consequence on what your character's icon will look like (all the 3d character stuff just generates an icon) mixed in with three questions of deep import written in a foreign language ("would you like your character to be a Mixlplk, a Jewwawwa, or a Flnobstrog?"). Good start.
Next, here's a game with an in game tutorial that takes over three hours to complete. (It took me two sessions.) The user interface (including the interface for the tutorial is terrible). As a simple example, the tutorial knows when you have completed a step but requires you to click "Done". If you click "Done" too soon, it tells you to complete the step. D'uh. I haven't seen this level of bad UI design since I stopped having to use Lotus Notes.
Oh and don't get me started on left- vs. right- clicking. The tutorial constantly tells you that "when in doubt, right-click". Guess what, many crucial game objects only respond to "left-click and hold". In general, the game uses three "noun verb" conventions: right-click and select from text context menu, left-click and hold (graphical content menu), left-click and click on some palette somewhere. These are all different and mutually incompatible, e.g. you can't "open" a cargo pod by right-clicking it. You can't "activate" a stargate by right-clicking it. Or maybe you can. Who knows?
The developers call the gameplay "open-ended". No it's not, it's non-existent. Everything is automatic enough to be no fun, but manual enough to be tedious. E.g. to fly from point A to point B you need to click on point B (almost anywhere, e.g. even on a mission briefing) and then (in one of maybe twenty different ways) select "Set Destination" and engage autopilot. Your ship will then slowly head over there ... unless it's docked. You can't start on a flight while docked. You need to click Undock and wait 30s first. (This is apparently too much for the Autopilots of the 53rd century.) Once your ship arrives, guess what? Your autopilot disengages somewhere inside the star system (not inside docking range), you need to click on your actual destination again and select "Dock", and wait a few minutes. Congratulations, you're Han Solo.
Combat is similarly thrilling. You see a red dot somewhere (e.g. in your "things in the vicinity list" or somewhere in space) and you click on it, then select "approach" or "orbit" and then click on a weapon. Then you wait and you either live or die. You can turn some stuff on and off if you get bored (e.g. your "shield booster" might slow your demise). Eventually, if you win, some cargo pods will appear. Click on one. Click Approach. Wait. Click on it again. Click Open. Open your ship (that's manual of course). Drag loot into cargo hold. Woohoo, now that's some flying!
Other folks have remarked on the thrills of space mining. Yes, you click on a rock, click approach, click your mining laser, open your cargo hold, and wait. Maybe your cargo hold fills, maybe you have to click another rock. Will you survive the excitement?
Oh and just so there's no doubt about how not open-ended the gameplay is. You can play "we got fired from E-trade because we can't design a GUI to save our lives" in space stations, and you can fly around in quasi-control of your ship in space. That's the game play. You can't walk to a cafe. You can't land on a planet. You can't board an enemy ship. You can't get on someone else's ship and man the guns while they fly. You can't negotiate loan refinancing with a blaster in the cantina. Heck you can't even book passage on someone else's ship to go visit another star system.
You can gain skills while away from the game. In fact, you pretty much can play the game while AFK. Most of the things you do are so time-consuming, you probably want to buy a GameBoy DS or something to pass the time. My newbie character has 13,000 skill points (xp) and 120,000 ISK (gold pieces). So I want a new spaceship. I find one (selling several star systems away) for 30,000 ISK. Now, can I get this sucker ... delivered? Nope, that wouldn't be tedious enough. Instead I need to fly over there (see two paragraphs back for the roller-coaster thrill ride that will ensue) and pick up my ship. (I can assemble and disassemble it with a single mouse click... new interstellar frigate 24,000 ISK. Fedex... priceless.) When I get there I discover I need a new skill to pilot it. No problem it's 4000 skill points. So I select the skill and click "Learn" or something and ... well I logged off when I had absorbed 500 of the 4000 skill points. And then I
Again, let me put this in context. If my level 10 warrior in WoW buys a new axe he may not be able to use it, but he can get it delivered. If the seller is in another town he might travel there, avoiding monsters (or killing them) on the way. He can go to the trainer and learn the basics of how to use the axe. If he doesn't have enough money, he can go kill bandits and get some money. So he can use the axe but he sucks at it? He can go "practice" with it on rabbits, cows, and giant spiders. All of this is to some extent "fun". Under no definition of "fun" will you find "wait six hours for a number to increment. The "benefit" of being able to learn "Gollante Frigate 2" skill while not logged on pales beside the benefit of being able to win Eve Online while not having it installed on your hard disk.
It's not surprising they can run 30,000 players on one server. This game is about as fast-paced and compelling as tic-tac-toe by email with a REALLY bad user interface.
Much has been said of the "gorgeous" graphics. Sure, like most MMOs, you can take some nice screenshots. I think the 3d artists have done a great job of creating 3d assets, and one day the programmers may get around to using them properly. E.g. when your ship accelerates, beams of light appear kind of where your engines are, maybe in front, maybe behind. Looks ... stupid. Space is full of really neat mist. Stargates look like giant guns that "fire" stuff to distant star systems, but the problem is your ship doesn't actually go into them. You go somewhere "near" them and then the stargate "fires" and your ship sits there for a bit and then fades away. The docking sequence is similarly brilliant ... e.g. you dock with one of the pretty spiffy looking space stations by flying up to it (or through it -- there's no collision detection worth a damn) and then ... the game seizes up and you reappear in space dock.
All of this for $20/month. Golly.
* You can win the game without knowing what the professions are. Just select "Unintall Eve Online" from Eve's main menu... no wait that's the Windows XP Start Menu. I get confused sometimes, but I should have realised it wasn't Eve's menu because it appeared instantly.