NOTE: The following response was typed today in another thread, but I'll post it here because it's also relevant.
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Okay, I'm going to make this lengthy as I will copy it and save it for future reference.
I am a Graphic Design (Art Major, Graphic Design Emphasis) student at the University of Wisconsin-Stevens Point. I have been operating for the first two years of my college education with a 400MHz G3 iMac DV (768MB RAM, 30GB external HD). To tell you the truth, it was okay. Not fast, but okay. I had been saving up to buy a new computer, and in March (3 weeks before a new revision) bought myself a 12" iBook 800MHz G4 (I added BT and AE). My logic was as follows: I was doubling my clockspeed, going from 768MB RAM to just 640MB (but the new RAM is faster) in addition to making a "processor jump" from G3 to G4, I was only 200MHz shy of the PB (at the time) *plus* I was upgrading from an 8MB video card to a 32MB video card. (Not to mention I was adding AE and BT and still it was cheaper than the Rev. B 12" PB.) So, I was getting most of the functionality for less cost. Also, the iBooks get better battery life, and are more durable. (That's what my research had told me)
So I bought the iBook. I was happy... or so I thought.
After just 3.5 months, I sold the iBook (and my iMac) and funded the purchase of a new Rev. C 12" PowerBook. And I have to tell you, It was a *very* wise move. Not only does the additional processor speed help with 2D work, but the video card doubled *again* to 64MB and I know that will help with speeding the OS up, in addition to the small amount of 3D work that I will be doing. The PowerBook is a much nicer machine all around. It's smaller, lighter, the keyboard is *much, MUCH* better (and I was completely fine with the iBook keyboard, in fact, I loved it!), battery life isnt' much less, and the whole thing is faster than I could have imagined with just the stock 256MB RAM. Now that I have an additional 512MB on it's way, I am very excited.
So, in short, I would have been able to save myself time, money, and stress if I had just gone with the PowerBook the first time around in March. But I'm glad that I waited, because now, AE, BT are included and standard. While I spent time carefully selecting my iBook configuration in March, when I bought my PowerBook, I walked into the local Apple Store, and bought the stock configuration.
I would reccomend nothing less than a 1Ghz G4 for anyone doing serious Graphics work. And I dont' mean "serious" as "intensive", I mean "serious" as "important, crucial" work towards your goals.