I have 900 MHZ G3 iBook that I still use everyday for word processing, email, internet and that sort of thing.. It works great.. The G3 iBooks (maybe iBooks in general, not sure) get GREAT wireless reception.. I have it maxed out with 756 MB Ram and it runs Tiger very well.. It may have been better to keep it on Panther, but it's comparable- the main thing is I don't think you want to mess around with Leopard if you go this route.. I could be wrong on that, and I'm sure there's plenty of people that have it installed and running fine, personally,I wouldn't do it..
Now the downside with the G3 iBooks.. The dreaded faulty logic board situation.. I'm sure you heard about the logic board repair extension program that Apple had for them, and the problems they were notorious for.. Unfortunately, that issue was not exaggerated at all.. Mine is on it's 4th LB.. It runs great for long stretches, and then it just dies..This really wasn't a problem up until now because all I had to do was take it to Apple, drop it off and in a couple days I had it back good as new.. Well, the repair program is over now, so if it happens again that pretty much means the end of that computers life.. Not trying to scare you away, just giving you my honest opinion of the G3 iBooks after 5 or 6 years of ownership..For me it's not really my main computer, so I live with it.. If I was planning on using this as my main computer I might feel different..
If you go that route there are pro's & cons.. You can get them cheap, and you can get a good one that will still perform decently for what you'll pay- but there's always that logic board issue looming over them..
Good luck with your selection- hope you find a good one.. There are some values out there- just gotta do a little legwork and get a little lucky..