I've waited for a while and today decided to see the Museum of Graffiti. I was very skeptical, but so pleased and engaged. The staff is very welcoming and shared information. The exhibits are well laid out, clear, and thoughtful. You cannot leave without gaining an appreciation for the graffiti and murals covering so many walls in Wynwood. If you're going to Wynwood, I'd put this attraction on your must-visit list. The gift shop has interesting stuff, too.
They have moved recently, so make sure the address is correct - it's just around the corner. The ticket might be pricey, but it's worth it. If you live in Miami and have a library card, you can get a pass!