14R, what was your Merc average? Or do you have an average for a full size bike? I know it's not scientific, but ballpark comparisons are interesting. Also, how is the spoke tension on your baby?
mcalpik, you are probably wondering why there are full size bikes out there that weigh 15 pounds, but your little bike weighs 20# with similar componentry and smaller wheels. The answer is the frame. I doubt that there are lighter wheels than yours on the market (unless you look at 355 or 349 wheels), but the diamond on roadbikes allows for featherweight tubing. So, even though there is more of it, it is substantially lighter than the Sonus tubing. The hinge is the biggest offender. Hinge-less bikes like Bike Friday or even what someone described as the "tractor-looking" Birdy would probably be (significantly and somewhat respectively) lighter with your componentry. Some Fridays weigh in at road bike weights. Somebody on the Birdy forum got one into the sub-8Kg range with Tune and American Classic components.
Of course, it sounds like you like a light bike for riding rather than carrying. (I'm the opposite; I'm a weakling and have to carry the bike all the time.) For that, there is some evidence that your lower profile is going to give you an advantage over big bikes, at least on a smooth tarmack.
For riding, I prefer strong hubs and wheels. I can bunny hop big potholes (if my safety latches are working and the wheels don't fold under the bike) or smack into them on my Birdy in ways I couldn't on the Mu. The fully spoked little wheels are strong enough to take significantly more abuse than big wheels.