Recently, I posted about how the Microcell didn't actually live up to its claims of fixing poor reception. As it turns out, it actually DOES work; you just have to know how how to set it up right. And judging by the plethora of negative tweets and blog posts about the Microcell, it's pretty clear that AT&T hasn't done a decent job explaining how to get it working.
The solution is actually very simple: move the device away from other wireless transmitters (I'd say at least 20'). This includes wireless routers and maybe even cordless phone base stations. The Microcell is naturally placed in close proximity to a router or modem since you have to plug it in to one of them to get it working. (It's ironic that the device ships with a very long ethernet cable, despite the instructions saying you only need to place the device at least a foot away from other gear.) I ended up plugging my Microcell into one of my broadband over power line (BPL) receivers in a completely separate room from my other networking equipment. Now the only issue is latency, but at least I'm not getting dropped with full reception anymore. Let me know if this works for you.