Just today, I replaced the stock clutch lever with an adjustable unit from Puig, the Clutch Lever 2.0. I have an equivalent brake lever on the way too. To replace the levers, you must buy two parts: the lever mount, and the lever itself.
The mount is model specific, and Puig does make it for the G310R, which should fit the GS, and apparently also fits the G650GS.
I bought both brake and clutch levers and mounts from Revzilla. Including state sales tax, it's around 200 dollars total. It's more expensive than the no name Chinese ebay specials, but I also did not trust the no name Chinese ebay specials.
Installation was a breeze. I bought the blue lever, which matches the blue G310R perfectly. I am absolutely thrilled with the appearance. I can also verify that the clutch lever will not interfere with the high beam flash like the no-name Chinese made levers, even when you set the lever at the closest position.
Overall quality is very good, and installation was pretty simple. There are 6 adjustable positions, from position 1 (close) to position 6 (far). The stock lever feels about the same as Puig's position 3 (see picture for a rough reference), so you can get a little closer, or farther if you're the type who can palm a basketball.
I put mine down to position 1 and found it just right for my relatively small hands. Previously, I had to really reach, and my shifts were sometimes less than perfect because I didn't have the fine control I wanted, and the engagement point is so far out already. Now, I have extremely fine, precise control. I'm less fatigued, and even rev matching to downshift is so much easier. Honestly, it feels like a whole new bike, and I haven't even received the brake lever yet.
5/5 - I really like this clutch lever, and I expect the brake lever will be just as good - it shipped separate so I'll have to wait a couple more days.