Let me preface this by saying that I find most museums boring, especially ones of modern art. Maybe it's just because I don't understand modern art, because I see no artistic value in oddly shaped objects or random things hanging off of wires.
That being said, I actually quite enjoyed MMoCA. It's much more manageable than most museums and you can see everything within a few hours; unlike other places with 5+ floors each displaying 10+ exhibits that take an entire day to traverse. It's also free, which is always a plus. However, it operates based on donations, so if you have some spare cash, please do donate.
I went on a Saturday morning and saw the Leo Villareal's LED lights exhibit, which was really cool. I also love how you can go onto the balcony on the third floor and breathe in the view of the city.