As a rider, I often give the "low-cool-wave" signal to other bikers as we pass. Seems a solidarity thing amongst motorcyclists - well most riders. There is the notable exception of riders of a certain American brand of motorcycle that unfortunately divides riders into an "us" vs. "them" thing (silly really).
Like others, I've noticed more and more Mo's on the road. But I haven't experienced the wave. I've seen others with appreciating looks, but no outright acknowledgement. Of course, then again, I do commute in the Washington, D.C. area where the most popular hand signal amongst drivers is the one-fingered salute.
This also brings up another issue. How do folks feel about more and more Mo's coming out both in a general sense and specifically to their vehicles? For example, I like the idea of the Mo being a popular vehicle. Confirms my good taste and helps to keep the demand for aftermarket options up. But then again, I also like to think of my Mo as being an original. Haven't seen many Black/Cafe Latte leather Mo's fully loaded (and I kind of like that), but hard to tell whether someone has the internal options from the road! I like all my vehicles to be somewhat unique in character from the outside. What do other listers think?