Mac OS X 10.1.5 is out. It works fine for me. It definitely seems a little faster. One feature it adds is that Carbon applications can now use Quartz for text rendering, giving you delicious smooth text. However, this isn’t enabled for all Carbon apps by default, as it can screw with typography. If you don’t care about stuff like underlines crossing descenders and fractional spacing changing, there’s a neat freeware hack which turns on Quartz in all applications. Yummy!
Update: Definitely faster. AppleWorks now launches in one second. You don’t get time to read the splash screen.