I have the (now-not-so-new) wave-pattern shifter, and it has worked well in all conditions. The cylindrical shifter it replaced was OK, but the wave-patterned shifter gives me better grip.
For me, however, the
positioning of the shifter has been the critical factor in its comfortable operation, as I've had to deal with some problems in my right hand which have affected my grip on the shifter. Here's the summary, which I recognize might not apply to your client, Dave:
> I have the first stages of arthritis in my two index fingers, and in 2014, when I began riding my Raven, I had a prolonged problem with pain in the base of my right thumb.
> My shifter is located on a Thorn T-bar, just below the right-central portion of my Raven's drop bars.
> At first (2014) I aligned the T-bar at right angles to the fore-and-aft axis of the Raven. That meant I gripped the (older-style-round) shifter with my thumb underneath it, and my index and middle fingers on top of it.
> That worked well enough until I took a three-week tour in Denmark, Sweden and Germany, which was full of headwinds and/or hills. I worked the Rohloff's range of gears a lot, and by the end of the tour, the base of my damaged thumb was very sore, so much so that I found shifting gears uncomfortable.
> I adjusted the location of the shifter by rotating the T-bar backwards, i.e., away from its right-angle alignment to the bike's axis, by about 30 degrees. In addition to the stress caused by my damaged thumb, I had noticed that my approach to my grip on the shifter was causing stress: I have wider shoulders, wide enough that, to grip the shifter as described above, I had to cock my wrist to the right in order get my thumb beneath it and my first two finger on top.
> By angling the T-bar and shifter backwards 30° or so, I found I could approach the shifter from a modified "door-knob" perspective: Now, the butt end of the shifter nestles in the pocket of my palm, and my thumb does not grip it but runs alongside and behind the shifter. I rotate the shifter with pressure from the fleshy part of my thumb (at the lower part of the shifter) and the slightly-fleshy part of my palm immediately below my index and middle fingers (this rests across the top part of the shifter, with my fingers crossing the numbered scale of the shifter, at at angle.)
> Since making that adjustment, I've had no discomfort at all from the shifter. I'd guess that, 90-95% of the time, I change gears as described just above. Occasionally--usually when the bike is at rest, say at a stop--I change gears by gripping the shifter between my thumb and first two fingers.
> I had a severe test of the suitability of my repositioned shifter ten days ago: On a mini-tour of the hilly back country N and W of Ottawa, I damaged a tendon in the back of my right hand, the one controlling my right middle finger. It was very painful for the first 24 hours, so much so that I couldn't grip anything with my middle finger. I first thought--jeez! how do I get home, if I can't shift gears? Happily, two things rescued me: I didn't need to use my index
or middle finger to shift gears (see above), and the condition began to improve, and is now not far from normal
Those considerations may not apply to your client's joints, Dave, but from my experience, I'd look closely at the positioning of the shifter, as well as the pattern of the grip.
Good luck, John