Jeb's definitely a more competent guy than his brother, but I disagree with his social conservatism a lot. There was an example I was gonna mention, but I didn't want the thread going off topic, so I'll give a lamer one: He made "In God We Trust" the state motto, which isn't a big important deal, but it still irritates me on a separation of church and state level.
I don't know too much about Connie Mack, but Wikipedia did say he opposed the PATRIOT ACT and the bailout, so those are two big plus signs... As a libertarian though, I'm sure he's done a totally justifiable good deed through Government regulation or intervention that I'll hate him for
That said, if Bush runs I think he'd almost certainly be the GOP candidate, because like others have said, he's just very popular here.