If Obama wins the nomination, I shall definitely vote for him over McCain. I think the ideal scenario would be to have a Clinton/Obama ticket so that there is someone to take care of business right away, looking to the possibility of sixteen years of Democratic leadership (eight years with Clinton followed by eight years with Obama).
Personally, if McCain wins, I will start looking to expatriate myself. Things are bad now after eight years of the Bush administration. This country will be going down the tubes if McCain wins.