I had a MicroCell and it was an utter P.o.S. - I'm in a "marginal area" where, with my iPhone 3G, I could move from one place in my house and have 2 bars and other parts of my house would drop to "no service".
I finally got an AT&T tech to determine the problem I was having and it's a design flaw of the MicroCell. The problem with the MicroCell is that it has the capability to "hand off" the call to a tower from the MC, but it can't do the opposite. So, if I moved to an area of the house that had 2 bars of service, it would hand off the call to the tower; however, when I moved back into another area of the house that had "no service" it could not hand the call back to the MC, and the call would subsequently drop.
Thankfully, the iPhone 4 (in a case) holds the calls much better in my house (yeah, I know - weird, right?) than the 3G ever did and I've yet to drop a call anywhere in my home.