I have Mac OS 10.3 now and I'm enjoying it a lot. I have the iBook dual USB with 640mb of memory and a 600mhz processor. Everything runs smoothly now, even before I installed the extra 512mb of memory. There are several other improvements in iChat, Mail, and Image Capture. Reading away messages in iChat is better and I'm hoping that sound quality in voice chat is better also. Mail has a cleaner look and supposedly has better junk mail filters (I never get junk mail so I wouldn't know). Image Capture has a new feature that enables you to share your pictures over the internet, and even take pictures over the internet using the computer.
I haven't used all of the features yet, but overall I'm pleased. I think it is well worth the price and anybody who liked Jaguar will like Panther even more.