I had the Kapture group sliding back for my arca to begin with, thinking that ground glass would be important. Once I started using a vari-ND filter with Liveview on my IQ180 I found I wasn't using the ground glass anymore, and I decided to try the rotating mount.
I've had it for over a year now, and have seen no issues with any of your concerns. I think it's very helpful in that rotating is effortless, very quick, and the sensor isn't exposed to dust and other issues (dropping?) when changing. A bit pricey but to me well worth it.
(edit ... Can't believe it's been two years this month since I bought the rotamount)