Panther

I'll do a quick look on the internet and see if I can find any user reviews.

Here's a good one that you should find informative.

OSnews: What to Expect from Mac OS X Panther 10.3

Butrflynet..
Thanks for your reply.

If you have a G3 it's much faster. G4 a little bit faster. G5 piss off. A great update, my iBook G3 is much Snappier with 10.3. Expose rocks. New Finder. A very solid update. I'm not pleased with paying for it, but it kicks ass. You should expect a speed bump from it.

I have G4. Well, I would try 10.3 (after some possible bugs are fixed).