McCain: Forceful, belligerent, goading, antagonistic.
Obama showed he's a stable, calming force, and thus ready to be President. McCain showed he is a bitter man, who clearly feels his entitlement (that is Presidency in exchange for 5 years in a POW camp) is being threatened by this young whippersnapper, and could only lash out claiming that Obama is not ready for leadership. McCain didn't sound as completely incoherent as I would have liked (and clearly knows a lot of world leaders and has been a lot of places), but the effect was still to seem like we'd have a cranky, irritable, hair-trigger presidency with him. It's hard to deny McCain knows a lot about the world, but it's easy to see that what he wants to do with it is limited. Obama's knowledge is less directly experienced, but his wisdom is much better informed.
I'd have been happier if Obama had knocked down McCain more, but on the whole his measured approach will probably be the right one. This debate will keep Obama's path upward.