I also have one in Chicago. I live in a AT&T deadzone so it's been really quite useful.

My only observation is that since the iPhone update that changed their signal level calculations, the reported signal level from the microcell within my apartment has dropped quite a bit.

I've been getting only one bar in my house, and so I asked ATT for a free Microcell. They, of course, balked. I then told them I would take my business to Verizon and they promptly changed their mind. Just installed it, and now get 5 bars (4 even in the basement). People note an improvement in phone calls. My iPhone finally works as a phone!

I got one last week in my apartment. Although my iphone would show 5 bars and 3G, I'd only be able to connect 1 out of 3 calls when dialing out. I'd get dropped calls galore. AT&T's network has really deteriorated for me in the last 6 months. It wasn't always that bad.

Anyway, the AT&T store wanted to charge me $200 for the Microcell. When I asked them what my termination fee was, they said $150. When confronted with the logic that I could pay less, and get a free phone at Verizon that will work anywhere (and not just my apartment), they sold the Microcell to me for $50. I've been happy with it so far. I still despise AT&T though, but until Verizon announces a global iphone, I'm stuck with AT&T.

I have set up a few of these and in my experience they work well where there is no tower signal or very little. In other cases where there was a bit stronger tower signal, the cell phone would often drop the connection when you moved near a window and the phone switched to the tower signal. I talked with AT&T tech support but there seems to be no way in these instances to program the phone to give the Microcell signal priority. This switch and subsequent drop would happen even when the microcell was sitting in the window less than 2 feet away.

Verizon offers several dual mode CDMA/GSM global phones including the Droid 2 and the BlackBerry Bold.

Link

Thanks for mentioning that phenomenon. I wondered why I would occasionally get only one bar.