I'm sure that there's some great EU material about Han, but I'm just personally not interested in the character beyond his role in the OT. It's a very subjective issue.
I agree that we could see a lot of great new places with a shadier character like Han, but I'd honestly rather see an original character explore those places instead. I don't know why, but I just feel like Solo's story has run it's course, and any further exploration in the form of prequels would feel like backtracking to me. You could probably say the same about Obi-wan, but I'm selfish. I didn't completely like he way he was handled in the prequels and I'd like to see him get another chance to shine. Plus, he's probably my favorite Star Wars character. For me, I think this is just a matter of unfounded, extreme bias.
Not to say that I wouldn't watch a Han Solo movie (I certainly WOULD skip a Yoda film though). It's just that I would rather see an Obi-Wan movie, first.