Yes, got mine back within 3 days of them receiving it (well, would have if I was in to receive it - but alas, was at work so had to wait 4 days due to it being a bank holiday)
Only shot reballs through it (well and about 20 paintballs) and it does feel smoother - I mean, it was running at 125psi before (confirmed with the pressure tester) and now is running at 90psi (again, confirmed with pressure tester) with 290fps.
Feels noticeably smoother when you shoot now - and quieter.
It DOES have some new o-rings on the bolt system - think 22x1 and 23x1 o-rings (or 23x1 or 24x1 - cant remember).
Some people who never have issues with the QEV probably won't care much about this upgrade, but those who do will love it.
Personally, I love it and recommend it.