Panther
First off I did have problems with 10.2.8, a brand new firewire HD I bought wouldn't mount to save my life.
However it works flawlessly with 10.3 (7b80). here some other details
Install is so much faster, an install without the languages took me under 20 min. Notable the the beginning screens are different, you have all seen the new welcome video, well the different input panels also do a "cube" rotation transition, neat detail.
The system itself is booting, and running very fast, and I have yet to run into anything with a bug (cross my fingers) All the programs I have installed have run fine as well.
Still waiting to see if battery life is improved on my Alum 15.
Thats about all I can think of at this moment.