Hey Sindre,
I'm not a programmer and cannot pretend. On the other hand, I am technical, and run company networks and computer systems for a profession. Day in and out I utilitize MANY programs, mostly personal and some business. I consider myself a software tester/improver (in my eyes, which isn't always the general concensus). I observe programs intuitivity, function, control, interaction, and over-all appearance. All of which for Subsonic have been par, if not birdie
It's obvious you know your sh*t

It shows.
I look forward to many great releases of Subsonic. Now that I have it I don't know what I would do without it. I would be very upset if I was forced to switch up to Apache+SQL+PHP+JSP+BLEHHH program to do the same thing yours and perform just as well.
As far as my suggestions go; never say never.
Seeking would be the ultimate for long one-track songs. But hey maybe one day it will happen; just like WinAMP support for SSL.
Having the remaining song time show up in the client or browser would be nice. It already shows how much time has passed, is there a function to take that number and subtract it from the song length? OR show the length of the song in the browser to get a good idea of how much is left? OR add an extra parameter to the search index function to scan the length of the media file?? (Again, I'm not a programmer). OR with CBR files, players can perform simple division of file size by bitrate and possibly determine the length of the song for display.
User-level folder access: I was thinking something simple like listing the available music folders in the user-setup tab and having 'Accept/Deny/Hidden' boxes next to the folder list. Or possibly integrating the users and music folders tabs.
VBR ID/display: awesome! LAME resampling, even more awesome!
THANKS!
Dave