So my best friend got a replacement Nexus recently. Sitting them side-by-side, his had 2 bars of 4G and something like -93dBm and 32 ASU while my new-when-received phone had 2 bars of 3G and something like -103dBm and 1 ASU. I ran a bunch of speed tests and other data pull exercises and the speed was definitely noticeable. I have come to the conclusion that the phone itself was poorly designed and constructed (at least the CDMA version was). Alas, I am hoping that the GS4 will be a smashingly good device when it comes out and I am ready to upgrade again. Other than the weak radios, I have been pretty lucky with device #3 but the experience has been a little bit of a letdown. Overall, I still very much enjoy the GNex and I love the pure Google experience but, at the same time, I am not a rooter/flasher and am looking at the next device to be crisp and awesome out of the box. I chalk this up to a learning experience.
That being said, another friend of mine and my son have the same device and haven't had any problems. Weak radios on both counts, but both still on their original devices and seemingly happy with things.