I set one up in my in-laws' house today and it's pretty remarkable.  Admittedly, I haven't used it enough to assess it's long term reliability (it's been running for about six hours), but what I've seen so far has just been a solid 5 bars of cell reception throughout the entire house where usually I had no services at all.
For those who don't know, the Microcell is a miniature cell phone tower that routes your calls over your broadband connection.  The few calls I have made and received so far have been crystal clear.
For what it's worth, I called (pretending to be my father-in-law) and asked if there was anything I could do about my complete lack of reception in my home (I already knew about the Microcell, but I played dumb in the beginning).  I told them that Verizon works fine in my home (true), and that I switched because my kids were on AT&T (also true), but that the sales person assured me that there was coverage in my area (there is, just not in my home . . . you can get a signal on the road just in front of the driveway or on the back porch).  The girl told me about the Microcell and said she could knock $50 off of it, bringing it to $149.  I told her that was too expensive and that I would rather pay the $125 early termination fee to switch to Verizon which would produce the same result.  But she said it would be $125 per phone, bringing it to $250 so I asked to talk to a supervisor to have the fees waived.  He was an ---uvula--- right off the bat, but quickly relented and said that he would give it for $149 and put a $100 credit on the account, making the final price $49.  Not too bad.