I have Lucky Labs' vinyl wraps for my iPhone's bezel - love it!
I don't know if it has anything to do with the wraps, but these are my observations. I did have an insignificant issue with the signal. Apparently, I'm in a strong signal area, so I haven't noticed the problem until I took my phone out of a Bodyglove case. I lost bars from 5 to 3 or maybe 2 when I held the phone with its "hot spot" in my palm. The case completely solved the problem, though.
The wraps I now have on my phone (and no case, naturally) got rid of the problem too. I tried to see if I would lose signal again, but I don't. It's not only in my home, I went out of course, and I only have the wraps and Zagg dry shield on the back covering my phone.
And it looks so cool with those wraps!