If you listen to Obama's reply - I don't think 'Joe the Plumber' was a major problem - and truly can't understand why the McCain campaign has made so much of it.
I put some cash on an Obama win back when Clinton was still in the running - unfortunately I didn't get great odds as I was rather late to the game. With the polls due soon, and Obama ahead by a significant margin, the concern is that people won't turn out as they see it as a 'done thing'.
If it had been McCain-Kerry, I would have been fine with it. But out of the two on offer, Obama is the guy. Prior to this campaign, McCain has always come across well for me. However, this campaign has got dirty. The low spot was lots of (admittedly disavowed) comments that Obama sounds a bit like Osama. McCain should have gone nuclear on his 'supporters' who did that...
To be honest, Hillary Clinton should've been less negative too - negative campaigning always makes me think worse of the person doing it.
Obama does have an air about him which is inspirational - it's Kennedy-like (and I know Kennedy had problems). It doesn't feel like 'just another candidate'.
Obama's campaign may not have been beyond reproach - but it has (at least from this side of the Atlantic) been the only one from the start which achieved, and maintained, a presidential air.
Much more so that the incumbent - but that isn't hard.
I don't want a president who knows everything. I do expect a president to be able to hold more than one thought at a time. I want a president who takes expert advice, processes it and is able to weigh the pros and cons.
In his response to Joe the Plumber, Obama showed that he knows you can't please all the people all the time - but what you do have to do is try and get a 'best fit' given the conflicting demands and restraints.
Sometimes - or more likely often - this won't result in an optimal solution for most of the people. An 'almost best' solution for most is better than a perfect solution for some.
You can't please all the people the time - and if you try, you'll please nobody.