I agree with Alex (and I was just teasing him), if I want to listen to a stereo audio recording then my prefered output is also 2ch (I don't use my receiver to warm up the other channels) ... and that is the beauty of WASAPI Exclusive, it will change the output configuration to match the number of audio tracks present - no button pressing...it just works. The downside Alex mentioned of WASAPI Exclusive is that you lose Windows Sounds (or other sound output) when your app has exclusive control of the sound card.
Alex, I take your point about various set-ups and uses, so this is not for everyone. FYI - My HTPC is connected to my Receiver using HDMI for both Audio and Video. I have configured Vista Audio Mixer for 5.1 (as the default) and have all my software apps decoding and outputing LPCM using WASAPI Exclusive as the audio renderer (JR WASAPI for Audio Files and Reclock for DirectShow playback). I use my HTPC for playback of all media types including Audio (CD, CD Rips, mostly in 2CH), DTV (can be in 2ch or 5.1), DVD / BluRay / Movie files (can be in 2ch or 5.1) and this is where WASAPI Exclusive is terrific as it will configure the output to the correct number of channels. The real problems it has solved for me is 2ch TV and Movie playback where the "blank" 3.1 channels stoped the Reciever using the Subwoofer for base mgt and the Center Channel for dialogue. At my age I certainly will not claim "goldern ears" and can not say that the quality between the available renderers is apparant to me. I do however easly notice the incorrect handling of 2CH material broadcast over a 5.1 configuration (edit: what being said even 2ch audio sounds "better" to me when the Receiver is just getting 2ch input not 5.1 form MC)
Thanks
Nathan