Uh oh, AAPL is down $4
In general, when Wall Street responds poorly to Apple announcements it's a sign either that Apple's announcements were lame OR that Wall Street doesn't understand the implications. Remember that the iPod announcement was received with yawns (including from me) and so was AppleTV. We'll see.
Going back to my reaction to the announcements at WWDC 2006 (last year), it still seems to me that Time Machine is a killer feature. Just ship it and have it not suck and I'm sold. Stacks is also a killer feature. At last, your desktop can actually look pleasant without constant maintenance. (It's sad how much time I waste clearing up my desktops on both Mac OS X and Windows.) I should point out that the Apple Menu and Tabbed Finder windows in OS9 are long overdue for replacement, but stacks do appear to be a very well thought out replacement.
Quick Look may or may not turn out to be amazing. It really depends on what documents are supported and how easy it is for third parties to build their own lightweight plugins (e.g. if I can preview 3d models from, say, Cheetah 3D via Quick Look, that would be great, but how likely is that?) Quick Look is eminently hackable though -- write a Quick Look plugin to do screen casting, for example (since it's unclear whether that functionality is available in iChat AV as implied).
The DVD player functionality looks like a really compelling feature, especially for the Mac Mini as home entertainment center. At last, one of the two most annoying things about DVDs (skimming through them to find something) appears to have been clobbered. Now all we need is a MENU button that can bypass ads.
Spaces looks like it will be amazing. I've got a license to Virtual Desktop somewhere (one of several free and shareware virtual screen apps for OS X) and I gave up using it long ago. For something like Virtual Desktop software, incredible attention to detail (like perfect Exposé integration and muting games in hidden screens) is essential, and this is where Apple can make a great concept that doesn't quite work available to everybody.
Again, the devil is in the detail. Yes, Vista has automated backups. So does the Mac. Do you think that this is the same as Time Machine? It's like when Apple added outline font support at OS level back with System 7 saying "hey, Windows has fonts too".