So far, the 360 has been an overall disaster. The early launch has really hurt them, but they still have time to sort things out. The system still has a decent chance to be leader in the US, but very little chance worldwide.
I think there is still a decent chance that the PS3 won't be the market leader this gen, but it'll take a combination of Sony screwing up (launch, price, blu ray, delays, etc...), MS getting its act together, and Wii being a quick/strong success.
I think we'd almost all agree that we expect the PS3 to lose marketshare next gen. I've noticed that many of our Xbox-loving friends like to assume that that marketshare will automatically go to the 360. In all likelihood, anything Sony losses will probably be split fairly evenly between Nintendo and MS. The two systems cater to two different audiences that both thrived on the PS2.
I have a feeling that the next-gen "winner" won't be crowned by hardware but by software sales.