The signal strength generally is good, sometimes it will drop off but mostly it is just the signal itself. (ie I keep the 4 or 5 bars but drop from 56 to 1 mbps).
No microwave that I know of - would have to be nuking a cow as this will die for 1 to 2 hours at a time.
Anything special I should look for in a signal booster? I have a radio shack around the corner... would they have them?