I got to play for a few hours with bot matches and MP, all with the Sharpshooter. At first, the sharpshooter was pissing me off and I was ready to sell it back. But I gave it some time, just like I had to do with MAG when I first learned to use Move to play FPS. After a while, it started feeling a little better.
My arms and hands did begin to ache, but after hours of testing/tweaking, I think I've found a good sitting position with the right settings to make it work...and it really works.
I think where I see an advantage with the sharpshooter is specifically in the way that the Move controller is kept level at all times. When you just hold a Move with your hand, it's much easier (imo) to get off center. If you can get the bounding box settings and turn speed settings to feel right for how much you personally feel comfortable swiveling your arms, it seems like it's less physical work using the gun.
Also, it feels much more intuitive to me when it comes to pointing than just holding the Move in one hand. Without the sharpshooter, it just kinda feels like I'm using the Move controller to move the reticule around the screen, but with sharpshooter I feel like I'm aiming at the screen. I don't know if that makes sense to anyone else, but it translated to me jumping right into online, not great at online FPS, and I was able to immediately hold my own (was first place on my team a couple times in a row).