We live in a high-rise apartment complex (concrete and steel construction).  We have Cingular/AT&T.  Our cell signal strength inside of the apartment is horrible.  Although we typically get 2 bars, the voice quality is bad (e.g., lots of static and the signal cuts in and out so that you only catch a few words at times).  Furthermore, we don't get a strong enough signal in the interior bathroom or the bedroom.  (The signal is at the maximum -- 4 bars -- when we step outside of our building)