Why bother with a file manager? WP8 already has THREE of them with varying functionality (more if you count email). 1) SkyDrive can access the cloud, 2) Office hub can access files in your local 'Documents' folder (phone only, not sdcard), and 3) Media hub can access your sdcard (media files only folks, thank you).
I'm joking, of course. Point is, its a learning experience for those that buy WP8 and, overall, seems fragmented.
Most people are okay with files existing behind a secure API (i.e. as Office hub already functions). They just want a consistent way to download, read, write, stream, rename, move, and organize...
SkyDrive is the best candidate for the job. Please, urge Microsoft to add local file browsing to SkyDrive (equal to Office hub, but with access to sdcard as well) so this thread can finally die.:crying: