That's the killer feature right there!
Quicklook and cover flow.
The new Alex voice - use text to speach when editing and proofing documents as an invaluable tool. This new voice is excelent for that.
Spaces - looks like I'll be using this alot more than I had anticipated (on my MacBook at least). Kind of like I didn't think I'd use Spotlight in Tiger, but that ended up being one of the most useful features for my workflow. I can even jump to another "Space" from within a full screen Parallels VM (on those few occasions that I have to fire up an old copy of W2K to run a couple of legacy apps).
The real question is - Aqua or Graphite??? I've swiched to Graphite. It just fits more with the new UI.
Hmmm... Perhaps time for a poll?