I take care of a mustang at the ranch I work at, and I love her! She's really good with people, and has tons of personality. Other horses on the other hand... haha well she always wants to mate with them.... :p but she is really great to work with. She's very in tune with body language, and if you know horse language fairly well, she's easy. A lot of mustangs are like that, though, i've heard. She's a doll to lunge, you don't need any equipment, just her and you. Riding her is good too, just don't be pushy AT ALL. She has weird quirks, though. Like when she gets nervous or scared she does a little tap dance and moves her feet repeatedly and puts her head down. Its kinda funny haha.
What I find interesting is that she never ever spooks, which I don't hear a lot of with mustangs. If I walk up to something new like its no big deal and have her stand next to it, she'll do her dance, then finally stop, and ever do it again. So she'll do her dance every once in a while, but never an actual spook.