First off, I recommend you take a look at his Wikipedia entry for the details but I'll summarize here. He's been governor now for just shy of 7 years so he's got a good bit more experience in that department than Palin. He came from the state legislature having served as a state Senator for 12 years. He switched from Democrat to Republican in 1998 so he could be perceived as a moderate but this is also the guy who prayed for rain on the steps of the state capitol in November of 2007. He's very publicly Southern Baptist and that would appeal to the teabag crowd.
His terms as governor have been focused on business and include a recent trip to Dubai where he (and 31 of his staff) spent a week on a trade mission in search of new jobs for Georgia and where he coincidentally criticized the handling of the wars in Iraq and Afghanistan. And while he's seen a few controversies including a questionable land deal that he failed to report, he's relatively clean as Republican politicians go.
The bottom line is he's white, Southern, outspokenly religious, has appeal to big business, a relatively long and untarnished political career, and frankly could bridge the gap between moderate Republicans and the fringe teabag crowd. And he's busy trying to build up foreign policy credibility. I've been watching him the last several months and I honestly believe he's trying to position himself for a White House run.