517's are a really bad idea for long term everday usage. They are designed as race day rims and don't hold up nearly as well as say a 225, 519. I had Rynos on XT's, but the weight really killed me. Then again I'm a small guy and can't generate the sheer power a lot of larger riders can. Right now I've got a set of 317's and 225's. The 317's are great as a lightweight disc rim and the 225's are wonderful. They've been strong and I'm impressed at how light they are for a rather mid-range wheelset. This is a good time to have a set of disc hubs laced up to open up your future options. Note that you CAN NOT use 517's with a disc hub though!