Subj. Currently you can only see downloaded files after they are finished loading. The ones which are currently dl'ing can only be seen in Android notification area, which is super unintuitive (also ff often put its icon there while there's media playing on some site so it isn't like you'd think to even check there unless you're absolutely desperate to find out what the hell is happening to your downloads)
Unless you know this you can easily start dl'ing same file several times and then end up with several copies(also, ff does *not* ask if you're trying to get the same file twice - another nuisance). Bonus points for doing this on limited traffic network, especially considering this only affects downloading of big files.
Why not just make dl window same as on PC, with current status and speed and time left? Even on portrait mode there's enough space for that.