I've been searching for a better place to post a review, but this seems like the best spot.
Jeff sent me an updated firmware for my XTBM a month or two ago and I just got an opportunity to install it and give it a try. The kit includes a single part (the new firmware kit) and an instructions document. The guide is short but contains sufficient detail to easily get the update installed. It's basically as simple as pulling the old chip and installing the new one and then moving a resistor (desolder, move, solder). This should have taken 10 minutes (mostly waiting for my soldering irons to heat up) except that I got impatient and tried to pull the resistor before I had removed all solder resulting in a broken resistor leg. The broken resistor was a 100ohm 1/4w resistor but anything between 47 and 220 ohm will work according to Jeff.
I tested the same couple components prior to update and after the new firmware was installed. The initial test resulted in noise being reported on the order of 0.1-0.3 but the new firmware reported nothing. Jeff confirmed that the new update should handle low strength signals better such that they won't be reported as noise and see them as valid, low strength X10 commands. The other thing I can say is that when initially turning on the XTMB after update, it took a few seconds to initialize. Afterwards, it felt like it started up quicker. This could have just been in my head, but it seems faster (displays the initial text sooner, gets to the signal strength quicker).
Thanks again Jeff!