I have had the "Pro" versions for a few years now, swapping between different bikes and other grips in the process. My findings:
1) the new elastomers that are in a single ring are miles better in terms of being able to setup correctly without getting the the elastomer jammed or cut. Installation is easier, and it seems more consistent overall in performance. This is a big improvement IMO.
2) I have had these come loose on rides (old elastomers), which is highly disconcerting and hard to reassemble on the trail. My multi-tool (Specialized Swat) didn't have the correct hex key in that case.
3) Currently with these on my hardtail, I definitely appreciate the feel more than when I had it on my full suspension. To me these play less of a hand fatigue reduction role than inserts or good suspension, but it's noticeable. You definitely feel a bit less directly connected to the trail - in a good way - through chatter sections. The rotation bit never bothered me even in full soft mode on the Pros. It's something you get used to really quick IMO.
4) They have a new grip that is more ergonomic, which I think could be of benefit. I always found these a bit too slim (I am on medium) in certain portions of the grip. I also don't always get along with the dual clamp setup on certain handlebars - with my hand seemingly on the outer clamp portion rather than on the grip. I have Ergons on my full suspension for comparison.
--Edit-- I should add that my original intent was to help with finger pain on chatter in fast sections (braking bumps, etc) as well as some arm pump. I broke my thumb and seem to have lingering issues with longer, rougher descents. When I originally bought these, they were for an Evil Insurgent (a size or two too small) - so lots have changed with my overall setups since then as well.