He'd be a great candidate, if he wasn't a Bush. I don't know if I could vote for a Bush again, like Andrew said, it reeks of dynasty too much.
I'm going to note that in the last eight elections, there has been either a Bush or a Dole on the national GOP ticket. In spite of this, the Bushes won 5 out of 6 times.
I'm also going to note that in Democratic side, it was very likely that Robert Kennedy would have won the nomination (and quite possibly the presidency), in 1968. In 1980, Ted Kennedy was at least a credible challenger to Jimmy Carter.
If the governor of FL had the last name Smith, and all other things were even, he'd be someone that we'd all be talking about.
There is a lot of possibility in J. E. Bush in the future. He's ruled out 2008, but I see the Senate or the VP slot as exceptionally credible.