I’ve been using it for feral and I’ve also done a few custom batch scripts to verify what the optimiser is giving me. I like sanity checks. 
As far as I can tell it’s been giving sensible results, if you get something which looks really wrong drop your addon export, from WoW, here and others can recreate what you’re seeing and then look into it.
Until 8.1 we’re pretty much haste whores though, even after 8.1 I suspect that will be the case. It will depend on what other changes they make though.
I’ve done a few tests with the remaining 25% haste bonus removed, but the rest of the spec how it is, and haste is still the strongest secondary stat but its lead is small enough that higher level items would mostly be upgrades. There will always be outliers though, like items with an even amount of the two lowest stats, which won’t be an upgrade.
I haven’t looked at the PTR data for a while, it still won’t run for me. At least it’s getting to the character selection screen now though, it just crashes on load, so no testing for me so far.