I've got 650 rounds through my 6 Creedmoor (Stiller Tac 30 in McMillan A5) with a Bushnell XRS mounted in the Spuhr rings, just over a year of shooting (load dev, practice, PR matches, PRS style matches and a PRS match) through all conditions. I didn't use the Spuhr ISMS because I wanted to get as low as possible.
I didn't use rosin and there's been no movement at all, although not much recoil in my setup. Repeatable zero if you use a torque driver. Beautiful machining and finish with a lot of mounting options for accessories like a cosine indicator, red dot mount, etc. They look really cool as well if that's important to you. There are index marks on the rings, not sure if this is the case with the mounts, which come in handy for positional shooting. This is truly top notch stuff but you would expect it with the price.
Only drawback with the rings I found is that I ran out of room on my rail to move the scope forward, so I have an extended rail on order. The level is a bit small, but the fact that it's built in and the kit comes with a leveling tool kind of makes up for it, as setup is a lot quicker and less of a pain. If you are far sighted, you may have trouble seeing the Spuhr level and may be better off with another system and running a scope mounted level further up the scope tube.
I use or have used Nightforce rings, ADM mounts, and 3 of my shooting buddies run Badger rings and LaRue mounts. I think that any quality ring set or mount will do just fine, but add the cost of a good level in and you are pretty near the cost of the Spuhrs.