Hello Leonid, I find the file module very well, just that it just misses something. I find that Canine Domesticus rightly, this message "Preview not available." gives the impression of a bug.
For the preview, I do not understand that it does not work properly, it's only an icon depending on the extension, I think we're asking for nothing more than that, and an attached image for illustrate and / or a cover.
Why not do it like downloading an article in market, (of course without the market-specific part), that would be great like that.