I live in a 3G only market, so I won't comment about the 3G/4G/WiFi handoff issues. My house is a bit under 2 miles from the tower, but I'm on the back side of a hill that blocks line of site. By point of comparison, ATT users frequently can't make calls inside my house.
I have always been able to make calls, but data was sometimes slow. The 4.0.3 radios improved data speeds, the previous 4.0.4 leak improved them again, slightly but caused voice call problems for me. I haven't had a chance to make a voice call so far, but the data speeds are the best I've seen so far. (as tested from my desktop PC tethered to my GN)
My speeds used to vary quite a bit depending on tower load (there is only one within range of my house) , weather, radio signal conditions. What I'm seeing right now is at the upper range of what I have EVER seen here. At this point I can't say for sure if I just happened to flash when the conditions were perfect or if my signal really improved this much, but last night and this morning's results are leaving me smiling.