On insider RS1 .67, and really like it. Been on RS for a while but I did roll to TH .494. Yuk! Awful. It felt clunky like Android. On the 950xl, it was an improvement over .107 as released with 950's. Again, you could have designed the OS yourself and done a decent job!
The RS aka AU, is a revelation on the 950 series. Smooth, smart and stable. It has unleashed the beast and the xl now performs how a device with those spec's should do. Yes there are niggles, but every OS has niggles. On my iPad I get app crashes, on my sons Android tablet we get even more crashes and lock ups on marshmallow, and he's got a nexus!
The RS / AU 1 update is very stable on insider. So much so, I use it as my daily driver on 4 of my company devices. 950, 950xl, 640xl and a 650. Not had a problem, compared to recent attempts. Considering RS1 has only been worked on for a few months, I think that MS have done a good job with it. Once this latest insider has been tested by the insiders, and any last minute issues have been sorted, it will hit OTA, and then everyone can see where this bumpy road is heading.