They still get the job done, and are reasonably cheap. The OP did mention a budget.
A Macbook might be faster, but writing is hardly processor intensive so it would make little difference.
If the OP wants to do other things, the a Macbook would be better, but for what he asked, a Powerbook would be fine.
Recommending a g4 at this point, to someone who needs it for the next four years, is silly. Even if he could save a bit (and the prices on those things are so bad that he really can't) it's not at all worth it to buy 3 year old tech when you need it for the next four years.
My advice is a refurb 2.2 ghz SR MacBook. A new 2.1 penryn would be great too, but you might want the SuperDrive.