I've had the MRX a couple of weeks now and I like it even though non-transponding traffic doesn't show, if nothing else it reminds you that you're not the only one in the sky even if you can't see anyone! As you say though, build quality is suspect, I had to get a new aerial and retaining nut after the first one just wouldn't stay on.
Also just got to read Rod's article - interesting stuff, Rod, and the combined unit mentioned including ADS-B and FLARM would be great in the panel.