Anderton
The only thing I'd add is that a Microsoft representative implied they would continue work on lowering Windows native latency and hope it will be equivalent to ASIO eventually. I think WASAPI is intended primarily to give consumers who don't even know what ASIO is a much better experience than MME. 

They'd have to punch out a few layers to match ASIO, maybe very near but I doubt they will match it unless they create a brand new format. End of the day MME is going to be more targeted towards tablets and phones, and that's how it will succeed.

WASAPI apparently offers little advantage over kernal streaming in terms of speed. It is not so much designed for users as it is for developers who do not have to write all the code themselves in order to get that low level access. One limitation is that it is designed to handle multiple data streams simultaneously. That is potentially an advantage for users who want to use multiple audio devices, but understandably, the performance of WASAPI (CPU load) takes a serious hit when it is asked to do so. The weakness of ASIO (one driver at a time please) is also a strength (don't dump your crummy data in my stream).