I, too have bought and built the original XTBM and have updated the firmware to a later version (don't know what it is right off hand).
I was VERY impressed!
The kitting... excellent
the attention to detail (like ESD protection of the micro, bagging the parts, etc.)... outstanding
the board quality and silkscreening... great
the price... VERY reasonable.
The effectivness at finding problems.... couldn't be better or more useful!
I fixed my father's and my problems and found some unusual signal suckers that made our X10 systems 100% (well.. maybe 98%).
FYI... my father's refrigerator had a BIG signal sucker!!! WHO KNEW?
Guess it was the electronic temp display and controller!
I would NOT hesitate to recommend getting this great item, whether kit or assembled! Even if you only use it a few times! It will come in handy later to diagnose a flakey transmitter or find an intermittent module's problem... if the signal is good enough or is it being "clamped" by something, or is there alot of noise from an item.