I'm having trouble coming up with a use case where I'd need the file chooser to do any of the things you'd want to do in the touch interface.
I can't speak to the music file thing because I haven't dealt with music files in years, it's always been an annoying and tedious experience for me (as is working with any large number of files with wonky metadata), so I switched to streaming and haven't looked back.
EDIT: That said, videos on my NAS just show up in the metro "Videos" app and I can watch them without issue. I haven't tried it with music but I can't imagine why that would be any different.
A good file chooser enables that scenario and generally, maximizes the benefit that Windows 8 brings to a tablet OS, which is the Windows desktop. If Metro can stream, read from memory cards, view files from Desktop apps, etc. the high purchase price of these systems would be justified.
For instance, Metro lacks a file chooser where you can easily find files anywhere in your system. If the Metro interface had a good file chooser, you wouldn't have to drop out to use the file desktop chooser to find a file on any filesystem.
If Windows 8.1 adds a good file chooser and if Microsoft addresses a few specific problems like that, life in Metro could get much better.
I hope Microsoft can get its branding straight -- I find it weird that I click on a music file across the network and it pops up in a pretty Metro app with the tag line "Xbox Music". There's also some thing (which has never quite worked for me) called "Xbox Games" which I'm not sure will do anything for me if I don't own an Xbox.
Or is everything that runs Windows 8 an "Xbox" of some kind? And how come I see tiles for all kinds of music except for the music that I've got in my own collection?