Glad you guys are enjoying the game. I think it's important to point out that Jonathan's comments about balance and campaign longevity refer to _Omega_ World, and aren't necessarily an evaluation of the long-term campaign viability of any of the previous Gamma World editions or the Gamma World post-apocalyptic campaign setting in general.
Omega World is really, really, really deadly. Most players will go through a couple characters during a campaign, and in some cases dying isn't such a drag because it's always fun to roll for more random mutations. Omega World stresses random die rolls much more heavily than the core d20 game, so that's another reason why things can go from bad to worse literally on the turn of a die.
Someone upthread mentioned that the game is a great d20 toolkit you can use to adapt earlier material. I couldn't agree more. There's just not enough room in about 45 pages to give all sorts of details on the Cryptic Alliances, for instance. New players can feel free to make up those details, while existing Gamma World enthusiasts already know where to turn to find the juicy details they'll no doubt want for their next campaign.
Keep up the feedback, folks. We love to heard how we've done (even if you don't agree with some of our choices)!
Thanks,
Erik Mona