Windows 7 has 3 media-playing platforms by Microsoft: Zune, Meida Center and Media Player. All of them have different designs and functionality. Many people miss codec support, for example flac is not supported. (There aren't any free options how to transcode
flac to wma lossless easily.) I would also preffer to encode/decode/transcode music and videos using GPGPU (DirectX 11, Direct Compute?). If you search something, there isn't a way how to search folder names. You have to go over the whole library and tag everything,
if you haven't done it by now.
In my opinion, there could be a "Zune - Media Player" where you could switch to a bigger design for TV's like in the Metro UI now. If some additional capabilities were included only for technologically advanced machines (faster transcoding using something
like DirectX 11), it would be great. The GPGPU could be included also with Windows Live Movie Maker and Photo Gallery. These tools would be way more powerful with it.
As many people have huge libraries filled with flac files. It would be nice to at least provide some kind of tool to convert all of them to a supported lossless codec easily within a few steps. Otherwise, people cannot sync their music to Zune or WP7.
You can do it! You have done something similar with the IE9. There you introduced HW acceleration too.