I doubt that many people would regret hitting the lottery, but I checked out Ben's stats today and not only is he playing fewer minutes than ever before, but he's scoring less as well, and generally seems to be just another bench player on the Pistons roster. If I was him, I would be thinking I wish I had taken less money to be a bigger part of a winning organization.
I don't really know if Ben would have worked out here with Rose, and I think that Korver could be useful, but it would have been interesting to see Rose play with Ben. Ben would have certainly had a ton of open looks given the attention that Rose draws, though I will admit a lot of Ben's usefuleness came with him playing on the ball. Starting lineup of Rose-Ben-Deng-Boozer-Noah would be a lot better offensively, with possibly Brewer off the bench to be a defensive substitution (or another defensive stopper at the 2, given our salary cap considerations).
I just have to think he sees what has happened in Chicago and has to be thinking he wishes he was still a part of it. His career is slowly descending into being an afterthought around the league.