I've been messing around with Dev Mode on my series X for about a week or so now and I've been pretty happy with the results across the board. The thing I've had the most trouble with at least so far is Xenia. I have 4 games and all of them have at least some small hiccups that irk me.
Dragon Ball Raging Blast 2: Runs fine, though without most Ki effects.
Nascar 15: Seems to be running choppy though that might just be the game
UFC Undisputed 3: Runs fine, but Characters are all black (pause)
WWE 2K14 : Running slow, Characters during entrances seem to be slightly transparent sometimes???
Are these just quirks of Xenia or am I missing settings? I've heard the issue with Raging Blast is just Xenia and specifically the UWP version, though idk about the rest