I run it and would never go back to standard! It makes it easier for me b/c when I'm going down the straight, I could keep my chin on the gas tank and remain tucked "underneath the paint" and my foot is the only thing clicking at the lever. so easier for me ergonomically. I can also upshift mid corner while hanging off, in a fast sweeper. Once you get the hang of it, backshifting, or downshifting, is superfast too, especially if you're a blipper. It's a very easy swap that takes less than 2 minutes.
standard, I felt, I had to move my entire leg just to get comfortable while tucked. You can't shift while leaned over to your left because you'll drag your foot. However, that being said, some roadracers still use Standard-Mat Mladin and Chris Vermeulen.