Yup, two days ago.
Deployed to one server and selected group of workstations (W7/W10, laptop/desktop combo). No problems, everything went well.
The only issue I've seen is in SEPM, Install Packages -> RU2 (4615.2000) WIN64BIT package got deleted. The rest of RU2 packages seem intact. I tried (re)adding WIN64 install package afterwards, after I've noticed this. Just in case. Package appeared in the SEPM alright, but was deleted again after a while?! But, as I'm most likely going to move all the rest of the client groups to RU3 in a couple of days anyway, I'm not bothered (much) with this.
Besides that, nothing negative to report.
No problems during upgrade from SEP 14.3 RU2 to SEP 14.3 RU3.However, after the upgrade under "Clients" there is a mix-up of Computer names and User names, which we hope will be fixed soonas it makes the "Clients"-part more or less unusable.