Finally took the L&M Solo on a dusk/night ride from work back home. Some feedback:

a. The mounting was OK. The velcro strap attachment to the frame is a bit of a pain since it needs to pass under the cable; I had some issues in terms of the strap hooking on prematurely when I was trying to pass it under the cabling. The mount for the headlamp unit has a big thumbscrew; it goes on quite easily and clamps securely.
b. Adjusting the light was very easy. The light can be swiveled on its base, rotated about a horizontal axis and the beam width can be changed. I tried the first two while I was riding and it was quite easy and intuitive.
c. Performance was excellent. The beam has a good reach and provided ample visibility, even during dusk.

Overall, I am happy with the purchase.