Is there a particular reason you're looking for AISO over WASAPI? On Windows 7, there's really no good reason to go with AISO in a non-pro-musician environment. It is flaky, requires hardware vendor driver support, and WASAPI has the benefit of offering a true exclusive mode.
I don't entirely agree with your dismissal of ASIO.
> requires hardware vendor driver support
If your soundcard or DAC doesn't come with a real ASIO driver, you just pick some other output method. If it does come with an ASIO driver, that may be a good choice. I don't see that it represents a difficulty for the user.
> It [ASIO] is flaky,
I've used ASIO with ESI and AudioTrak soundcards for several years on an XP PC. They have been very reliable. Drivers are specialized software and some hardware companies don't put enough effort into developing and testing drivers.
There are still a fair number of reports of flakiness issues using WASAPI (even with MC!). Computeraudiophile.com has such threads. It takes a while for software behavior across interfaces to become well understood. When Microsoft changed the audio driver model with Vista, it took a long time for soundcard and DAC manufacturers to struggle back to having mature drivers.
> WASAPI has the benefit of offering a true exclusive mode.
And real ASIO doesn't? Perhaps you could explain further.
Bill