Clean and very friendly, with amazing donuts. The "Master" part of the name is quite apt.
Master Donuts has a large variety of donuts, including the classics like glazed, apple fritters etc. I was pleasantly surprised by how clean the shop was.
Note they accept cash only (as with most donut shops).
I enjoyed every donut I tried, none of them were very heavy, greasy or glaze heavy. In my opinion the best ones are:
Bear Claw: huge, like a real bear's claw only with apple filling and no nasty scratches and cuts!
Apple fritter: a bit on the crunchy side, could use more apple
Cinnamon roll: succulent with the right amount of cinnamon
I'll mention the good old classic donut by itself since it was the best one I've tried in Las Vegas: dense and chewy dough yet fluffy without being overly greasy. Perfect amount of glazing.