Anywho, it is worthwhile. Spotlight is faster and a lot more useful if you are looking for an app.
Time Machine is good if you find backups to be a PITA because it does the backing up for you on an external drive.
Stacks, while a minor feature, are useful if you group your applications into folders and make stacks of those folders, my dock is a lot more compact now.
If you use Boot Camp it's semi-manditory, since you are deprived of much needed driver updates otherwise and the tool no longer works. (bastards!)
The preview button is nice, combined with coverflow browsing pictures is easier.
Spaces isn't all that attractive, I used to like multiple desktops until I started using Expose and things that mimicked it. Now I just open everything in one great big pile of windows and use expose to find my apps. Probably useful for people migrating from windows who aren't used to expose and people from linux who have used multiple desktops.
There's finder improvements, but they just annoy me.