I have the first edition 300 mhz iBook with 288 mb of RAM and OS X installed. It seems to run quite well on my machine. I do have the OS X 10.0.1 update which did make a big difference in speed and seeing as how you would have a faster one, I am sure it will run just great.
I'm running it on a 300 mhz iBook with 192 mb RAM and it runs beautifully. No problems to report. It is not for amateurs though, yet, so don't get upset if you have a pile of peripherals that you expect to work immediatley and they don't. For day to day use it is wonderful though. I use AppleWorks 6.04 and IE 5 all the time. They work great. It is fun learning to use the Terminal window to tweak things. I also recommend Fire, if you are into using an IM client. It works perfectly as a replacement for my Yahoo chat program. I can chat with my Yahoo buddies and the app actually works better than Yahoo's app for OS 9, which they have not updated in way too long.
I have an iBook 366MHZ Firewire. Not too impressed. Very unstable with OS 9...OK on OS X but I would not recommend it. If you can only afford an iBook I guess I'd say go for it, but if you can some how fork over the rest for a titanium, there is no excuse.