Political experience is important only in that it is the only way we, the voting public can look at a candidate and begin to guess what kind of a President that person will be. I don't think there is anything which can prepare someone to be the President of the United States except perhaps some sort of service in a high-level executive job which deals extensively with both foreign and domestic issues. In that vein, none of the candidates really have any experience.
When I look at McCain, for example, I have 35 years worth of a track record. I see a man who generally votes with the right-wing of the party, but is not afraid to occasionally break with the party to pursue his own agenda, McCain-Feingold, for example -- something most Republicans were strongly against. He also co-sponsored the much-dreaded 'comprehensive' immigration reform bill last year.
Unfortunately, McCain of 2007 doesn't look a lot like McCain of 2008. He hasn't to my knowledge repudiated McCain-Feingold, but, according to Media Matters,
http://mediamatters.org/items/200808130004 he has since repudiated his former co-sponsoring of the immigration bill. I think this dash to the right wing of the party is a mistake which makes McCain look disingenuous.
I think what attracts me to McCain more than anything else (yes, I'm a cynic) is the fact that he's a Republican and that for the foreseeable future, both houses will be Democrat-controlled. 4 more years of gridlock is preferable to me when I think the wrong kind of change is the only other option (I say that in reference to the policies Obama would have a decent chance of getting passed, if elected).
On the other side of the ballot, we have Obama. I don't think the lack of experience is a terribly troubling item, and I think he's perfectly capable of doing the job and dealing with foreign leaders. I think he may have said a few naive things along the campaign trail re: foreign policy, but either President will have a bevy of national policy advisors to help him along, so this isn't a huge concern to me.
The most strikingly positive thing about Obama is that he is at the head of what looks to be one of the most well-run campaigns in our nation's history. Even if his message is crafted by the best in the political game, Obama can deliver it like no other. He's achieved this 'celebrity' status because of his ability to connect with people and be charismatic. By being part of such a well-oiled machine, Obama has shown that he either is an amazing leader, or has employed some amazing leaders to run this machine of his. I think that running the executive branch successfully takes many of the same qualities as running a good campaign, so I have no worries about his ability to step into the job on day one and be successful.
That said, I am not a fan of his stances on foreign policy, his tax code, his social security policies, his health care policies, or just about anything. My problem with Obama has nothing to do with the man and everything to do with his politics. I do, for what it's worth, think he's far and away the more genuine of the two candidates in that he probably believes what his writers are putting in his speeches. The new McCain is far and away, IMHO, more of the "empty-suit" between the two candidates.
The empty suit doesn't scare me as much as the liberal wing of the court having a solid majority though. There's a good chance that at least one conservative justice won't live another 4 years (an even better chance one doesn't make it 8 years) or that Kennedy retires. I prefer legislative gridlock, and perhaps a solid conservative majority on the court to any real 'change' proposed by either candidate.