Well.. PC and Mac versions are not interchangeable. If you own a license for the PC version it won't run or install on a Mac at all. You need a Mac version, which you'll have to purchase. Is it worth the extra ~$600 to have it on the iBook.
I have 2 iBook G3s... They barely run OS 10.4. In fact they are so slow they are practically unusable. However, OS 10.3.9 runs just fine on both the iBook G3s. Since CS4 requires OS 10.4.8 as a minimum, I'd say yes you could run CS4 on an iBook G3 if you install OS 10.4.8 or better. However, I don't think it would be at all usable.
I have both the PC version & the OS X version ( my job supplies me with software ). So the issue of the platform is not an problem.
I am running 10.4.11 just fine on my iBook G3 & I don't see any of the slowness that you seem to be seeing. But I have also upgraded the RAM & the HD, so maybe there is the difference.
Well, my iBooks are max'ed out with RAM and HDD space. 10.4 on an iBook G3 is absolutely nothing compared to MacPros and MacBookPros. Its like comparing a bicycle to a Lamborghini. Maybe I'm just spoiled. The only thing the iBooks are really good for is OS9 and those apps.
To the OP scott is comparing the g3 to a Macintel and to you it might seem like it is working fine but it has to be really slow.
I have done some test on the ofd G3 I had, which was a desktop with a GB of RAM and one of the test the G3 was 37 times slower.
but not until I upgraded did I understand how slow the g3 was.
So to you it will normal and to Scott impossibly slow.