I took the plunge today, and bought myself a Logitech G9. My old G7 bit the dust, and my 518 was flaking. The rubber was all coming off the sides.
Sadly to say, the G9 is made of that same kind of rubber so it's only a matter of time before that happens to it. Regardless of that, it's pretty comfortable. I'm liking it, but I haven't tested it with any games yet.
Edit: oh, cute. There's even a dry hard grip that comes with, and digging through the box reveals a cute little aluminum box with weights in it.