I think it's more interesting to try to make a case for somebody you won't vote for. Forces you to put yourself in others' shoes. I'll try:
He doesn't seem as simple-minded or beholden to Cheney-like father figures as Dubya, so I don't think he'd fall for War On Evil type of arguments that get us into Iraq-like quagmires. I don't think he gives a damned about Iran, which is fine with me. He strikes me as the sort who takes foreign policy seriously (and always in terms of trade), which mean maybe less of the John Bolton-types and more of the Jon Huntsman types in diplomacy. I think he'd rather have realists work for him than ideologues, because he knows personally how easy it is to fake being an ideologue, and how much talent it takes to have true competence. I think he's both a great fake ideologue and a truly talented individual, and those types know the value of their kind. But that's just my gut instinct.
For most of his political life, Romney has been a pretty moderate-to-liberal Republican. He was a friend to the gay community, pro-life, and not anti-gun but also pro-Brady Bill. He was governor of one of the wealthiest, most liberal states in our country, that's 14th in the nation in population. So he was responsible for running a pretty big budget (ie, he's no Sarah Palin). So you can definitely argue he knows how to get along with Democratics to pass meaningful legislation. The signature bill he'll always be remembered for is Universal Health Care, which is also the model for Obamacare. Even though he renounces it now, its example may be the only reason Obamacare was ever allowed to pass, and so it may prove more lasting than any other major policy initiative of his career, even if he wins the White House. It's certainly one of the most important pieces of state legislation (in any of the 50 states) passed in the 2000's.
He seemed to do a pretty competent job of organizing the Olympics in Utah, although I don't know that "event planner" makes him more qualified to be president than "community organizer." *wink wink*
Many view his corporate experience as a path forward for running our country, although it can be difficult to see how the lessons of outsourcing/closing factories/laying people off can apply directly to killing bad guys or delivering checks and services to old people (the two primary functions of the modern federal government). The two most prominent CEO-turned-presidents aren't remembered so fondly (GWB and Hoover), but there is something to be said for running large and disparate organizations.
His father was a very prominent politician in his own right, although again I'm not sure the dynastic argument is a pro or con in terms of ideal presidential candidates. Much like the Clintons and Bushes, his family is well-connected.
If the 2006 version of Romney were running today, I'd be quite comfortable in voting for him. Since then he has taken a very, very sharp turn to the right. Some feel this is really his natural inclination and that Massachusetts Mitt was a charade, while others think the current "strict conservative" Mitt is the charade, while still others feel like there is no real Mitt but only whatever Mitt it takes to be successful. I think the third option is the most likely, and I oddly take some comfort in that.
I have a gut feeling that once he finally had all the power he wanted, he'd pretty much exercise it to get people to get along. The man clearly cares about amassing a legacy, so unilateral massive tax cuts/deregulation is a non-starter while Democrats can still filibuster. Romneycare makes me feel like he'd rather pass legislation that actually accomplishes stuff than win ideological battles that have little tangible or lasting real-world impact. In much the same way that Nixon could only go to China, maybe only a "strict conservative" as the current brand of Romney could get away with moderate policies that can muster some bipartisan support. *shrug* It's a hope at least.
That's the best I can do. I'd encourage the conservatives on this board to try to put together their own arguments on the Obama thread. I personally found the exercise both interesting and oddly reassuring.