I've got a first gen 17" iMac G5, and have been very happy with it. I'm using it with an external 19" LCD, with the screen spanning hack. Works great.
2 minor complaints: video chip is kinda weak, and I need more HDD space (80gb now, thinking of upgrading to a 300gb at some point). I think the current version solves these problems well, and adds some nice features.