Don't miss him at all.
He was highly over-rated, and happened to come into the UFC when the HW division was in shambles, and was able to win the belt because of his size and wrestling. If he came in the UFC now (or even 1 year ago), he wouldn't win the belt. He just doesn't have the skill level to compete at the top level of the sport.
If his career wasn't fast tracked by Dana he may have never won the belt either. Once the blueprint on Brock was known (that he doesn't react well to being hit), his career went downhill pretty quick. If he had to take a few more fights on his way up, that blueprint may have come out a lot sooner than it did. Brock was able to use his size and wrestling over physically weaker and smaller opponents at the start of his career. Once he started fighting bigger guys that could stop his takedowns and he had to stand (Carwin, Velasquez, Overeem) it was clear how bad his stand-up was.
He never deserved his title shot, and while recently we've seen a number of undeserved title shots, I don't recall nearly as many back in the "pre-UFC 100" days. Mir beat Lesnar at UFC 81 vis submission. Lesnar beat Herring at 87, and gets a title shot at 91, while Mir was sidelined from his win at 81 until 92 -- the event after Lesnar was basically handed the title from an aging Couture.
Beyond that, I just don't like his personality. He's cocky, thought he was better than everyone, and was a sore loser. I thought his UFC 100 interview was bad for the sport, and just found him to be a genrally unlikeable guy.