Well, I just got my HD500X to replace my soon to be on Ebay HD500. I must say that I am pleased with being able to add 63 Reverb to some dual amp presets I had before that wouldn't even allow me to add ANY reverb! Might be only 20%, but I'm running 8 effect slot fully loaded dual amp patches with any reverb I choose.
Now if they would just throw out a token firmware update that added some new toys (particularly amp cabs and mics, maybe an amp or two).
I do actually like the new switches. Definitely feel a little more rugged than the other ones when depressed (although I never had a failure on either one of my HD500's in the button department).