I'm not sure what to think about signal. I often see 4G with what looks like zero bars. I go into About | Status and it lists -115dBm. Now, I only have the OG to compare it to, but on there, -115 was pretty much dead. -120 was the number that gets filled in when you are in Airplane Mode.
Now, even with zero bars and -115dBm, I have signal. I can use the phone fine. I opened up "Speed Test" and got something like 6mbps - with what I thought was no signal at all. With full 4G signal I was seeing over 20mbps.
A couple things to note. I remember reading about a signal measuring issue. The signal strength you see in the about screen on the Nexus is the signal of the 4G radio if you are on 4G, and the 3G radio if you are on 3G. The claims I read said that on other pre-Android-4.0 phones, the About screen will ONLY show the signal of 3G, even if you are on 4G. And I think it also claimed that the number of bars was based on that number as well.
So by that logic, you can compare 3G to 3G apples to apples, since both phones will be reporting signal strength and "bars" in the same manner. But when they are connected to 4G, other phones will continue to show the 3G signal strength (which is higher, as you'd expect)
Anandtech Article here is a very good read and shows very clearly that you just cannot compare the different 4G phones until they are all running 4.0 or if you have access to a service console
AnandTech - Investigating the Galaxy Nexus LTE Signal Issue
Droid-Life summarizing the article somewhat:
Galaxy Nexus LTE Signal Is More Accurate Than Others, There May Be No Problem – Droid Life
Now here is what scares me. It sounds like Verizon is making an update to the Nexus to "make it more like other handhelds". Does that mean it will now show 4G with signal bars for 3G?? Time will tell, and hopefully the AOSP roms will revert that change and give us the accurate display instead:
Verizon Confirms Galaxy Nexus Software Update, Will “Adjust Signal Indicator” to Better Match Other Devices – Droid Life