I also purchased one of those clearance Mark IV barrels. It was very affordable. And while it works just fine with a red dot, I often wish it had sights simply because I'm not the biggest fan of the red dot sight systems on pistols.
Perhaps I'll get used to the red dot with time. I'm not sure how I would like open sights with such a short sight radius anyway...
Edit to add: That short 3 1/2" barrel is considerably louder than my pistols that are 5" and longer. That short barrel really barks without a suppressor.