I would not attempt training Mustangs myself. I have a hard enough time with a colt I raised. HOWEVER, with proper training they can make awesome horses!
I own a BLM Mustang that I bought already well trained. He is, hands down, the best trained, safest, most respectful horse I have ever owned. He is the horse you stick guests on for safe keeping, no kidding! He was 12 when I bought him and he's 20 now. He has a home for life here.
But, I had no hand in training him, so I can't take any credit.
Smrobs, another member on here, has some really nice Mustang(s).
I definitely wouldn't recommend raw Mustangs out of the wild as first horses though. I wouldn't recommend ANY untrained horses as beginner's horses.
Some people have confidence and seem to skate through life without trouble finding them. Everything comes easy. But I am not one of those!
Here is John Henry, BLM Mustang and trail horse extraordinaire. Actual wild Mustang in the background.