I've read it's buggy, slows down the phone, and is a resource hog. Haven't messed with for a while and disabled on earlier AT&T phones, but now I have an HTC One M8 Unlocked version, so no AT&T crapware for me.
I guess for a free 50 Gb I'll deal with a bit of grief if I have to. So far I've uploaded a bunch of photos with no real issue. When they begin to charge for this as a service then I'll think twice about what to do next.