So is the ad any good? It depends. The windfall profits tax is a dumb idea, and I wish Obama didn't support it, but I guess politics is politics. It's not the biggest deal in the world.
More important is the basic message of the ad: McCain is in the pocket of big oil interests, just like the Bush/Cheney gang. As a one-off, this probably doesn't have much impact, but if it's a harbinger of things to come — and I assume it is — it holds huge promise. It's just like McCain's legendary series of flip-flops: on an individual basis they don't matter too much, but when you put them together into a coherent narrative they make a powerful story. After all, pretty much every McCain flip flop has a single source — changing his position to be more acceptable to the anti-tax, big business, Christian conservative base of the Republican Party — but nobody gets that unless you put them all together and then bang them over the head with it.
So this is, I hope, just a taste of things to come. If Obama bangs away on why McCain has flip flopped so much and who benefits from virtually every one of his changes of heart, it makes a great story. Stay tuned.