I've been using T3 since it was released. Everyone will have a different opinion on media management. Here's mine:
I like it. I know that it takes 5 minutes to rebuild the database if I make a change, but I don't make changes all that often so it's not a real issue for me.
On the music screen there are two buttons to select sort/filter method for music (genre/all music/video etc), and a box for displaying the results of this filtering. I'd like this real estate back on the main screen, so I'd put those items on the pop-up that launches from the search button.
Those sort/filter buttons: I don't like how I can't remove video from the option list. I don't have video and I don't want to have any indication that I have hardware capable of video.
With the FM radio and the GPS, I'd like to be able to hit the menu/minimise etc buttons. I'm almost guaranteed that the little toolbar will cover up exactly what I need when I minimise radio and GPS.
The control that users have over FP is great, but the settings screens are poorly organised and documented. Sometimes I can't find a function that I'm looking for or can't understand the ones that are there, and I've been using it since release (SEARCH N00B!! :) ). I only figured out a month ago that BBAA means Browse by Album Art. I presume that you're dealing with this anyway as part of the re-write.
I'd like to be able to add custom apps to the menu screen, rather than go to an apps screen to access them. One less click.
I don't like how I can't show track information and a vis at the same time. They are embedded in the same thing, and I can have one or the other.
I don't like how vis don't work with OGG files, but that's a WMP problem I suspect.
Oooh. Long post.
I hope the above is useful. I've been using FP exclusively because it's intuitive for me and it has a database. Please don't mistake the choppy sentences above for unhappiness - it's passion. :)