Tiger's a long way away from the absolute mess it was at the 10.4 and 10.4.1 stages, but I do wish I'd saved my money. Spotlight is incomplete and flawed, Dashboard is a waste of time and space, and Automater is just too complex - valiant attempt to simplify scripting it is, but it's sadly just not simple enough for even a geek like me to be able to perservere with.
The new Mail app has very few new features that I actually use (along with a hideous UI), Quicktime 7 was released for Panther too, I've seen about three apps that actually use Core Image (none of which I've actually wanted to use), and I haven't actually found a single app that I use on a daily basis that I wouldn't have been able to use in Panther.
But, it's my fault - I was suckered into the marketing, I bought it, and I regret it. The next time I upgrade OS X will likely be with a new machine.
Panther was so much better a release in terms of improvement over the previous release it was untrue.