I use it daily with T:ANE but I don't use TANE's editing folder.  I keep my assets under development in a set of home folders, as defined by AssetX, and just drag and drop them onto a T:ANE CM window.
There are a few problems:
1.  AssetX cannot yet validate config tags against the new variations in T:ANE.  There are a few that I have spotted.  If you just make content to TS12 rules then that works fine.
2.  T:ANE doesn't have a visible TrainzUtil so calls to TrainzUtil in T:ANE don't work.  There are a few scripts I use that just call TS12 instead.  Some scripts, like getting a next KUID, obviously don't work.
So it can be used for content creation but without all the features.  I believe Ian Woodmore has been using AssetX extensively with T:ANE.
I'm sure Andi will update it once information is available.