Los Angeles, California here on AT&T - nothing but great signal. I've gone deep into the computer labs here where most phones get no signal, but the N9 has 3 bars pretty consistently.

WiFi is a different matter and sometimes the signal seems to be a little weak, but I am comparing it to a Lenovo laptop with a more powerful antenna encased above the screen, so maybe that's it. I think improvements to WiFi reception are supposed to be part of PR 1.1 though.