I've had both the NS4G and now the gnex (with the NS4G the signal was a common complaint especially right after release last year, the forums even got kind of ugly over it). However, I've never experienced any signal or gps issues with either device. Maybe that is very area dependant? Don't know. There is also a photon in the household and that's a phone regarded as having some of the best radios in it. Since getting the gnex I've compared in areas that were marginal and found no distinct differences. I don't disagree that some see these type of signal issues but whether I'm just lucky or what, not sure.
Careful with the thought of just going with the new EVO, I'm sure that phone will have it's own set of issues (as every phone seems to). We just don't know what they will be yet.