The nice thing about the Fallout setting is that it has many elements in common with Gamma World. In fact if it were to be compared to D&D, traditional Gamma World would be the Forgotten Realms while Fallout would be more like Greyhawk. I think D20 modern might be a good way to handle the setting, but so too would be the just released Omega World.
The fact is that Fallout is a small chunk of the US after a nuclear hollocaust, and it has rules for mutants, ancient technology, and radiation. The only real difference between that and Omega World is really just the specifics of the setting. Of course since Omega World is lacking many specifics, there's really not a lot that needs to be fiddled with. Maybe create a new player race or two, and you're effectively there. Heck, the brotherhood of Steel armor is pretty much covered by Relic Armageddon armor.
To answer your question, yes, I am planning a semi long term campaign in a setting containing many elements from Fallout using Omega World rules. It would be interesting to convert the perks from Fallout to feats if they haven't already been covered.