Interesting article comparing six different ajax frameworks, everything from GWt to Atlas to Prototype. Pretty informative. The long and the short of it is that none of them are perfect and all of them are immature.
Don't you hate when they say they've released books but you can't buy them yet? What does that mean? That they've released contracts to the authors to write them? GRRRRRRR. I want 2 of these books!