Everyone I know has a sub $100 USB interface hanging off their machine and swears constantly at the latency and wishes they'd just stuck with ASIO on Windows...
Personally I still have a workstation...
As for the iPods they sound horrible. The latest line of nano has noticeable noise on the outputs.
USB interfaces are a terrible idea - they are polled and add latency every time.
You're complaining about WDM audio. There's built in WaveRT and external ASIO stacks as well. The latter has become the standard on Windows for professional audio and is direct hardware access.
USB audio devices are and aren't polled. The cheap ass speakers and stuff are but anything $20+ are buffered raw device access.
I can get 8ms out of a Windows 7 laptop with ASIO over USB that isn't even tuned. My Korg Triton Studio manages about 4ms and that's seriously high end kit.
WaveRT is what WDM uses, right? With the associated delays going user/kernel mode. How does that help?
And USB devices are polled, at three levels as I recall - 'control', 'interrupt' including 'isochronous' and 'bulk transfer'. The frame interval depends on the USB speed - and I see they are sub-millisecond. SO very adequate for audio sampling. I used to use it for serial protocols, and that frame rate was entirely inadequate for signalling so I formed my low opinion of USB at that time.