I thought I'd compile a few things here, instead of just separately listing feature requests.
First I'd like to say that subsonic is great, and although I appreciate this is originally meant for audio streaming but also allows video streaming, it is the best video streaming server I've found, tested and approved:
1) web streaming through flash (and hopefully html5 soon enough)
2) user accounts and login
3) monitoring user activity
4) chat
Plex is 2nd best in my view for video streaming, although it's strictly limited (no user accounts/login except when using myplex and publishing the server, which requires open access to network and wouldn't work within closed network), and is therefore NO GO!
Feature Request #1
request: Video seeking for on-the-fly transcoded web streaming
comment: I note there's been a number of discussions on this issue, but not properly addressed within the server itself.
Feature Request #2
request: player support for subtitles, multiple audio streams, multiple video streams
comment: Subtitle support would allow 1) external files with same name; and 2) mkv files that contain subtitles. Video streaming would ALSO have to allow options for selecting subtitle (not sure how the player itself would work, but I assume that each time a subtitle is selected this would require changing the transcoding settings every time to set the arguments to process selected subtitle, and restart transcoding at the point where the video was?). Similarly to subtitle support, player would allow choosing which audio or video stream and transcoding settings/parameters would change accordingly.
Feature Request #3
request: Metadata support for videos retrieved from anidb, tvdb and the likes
comment: I do already appreciate how we can "google" artwork and replace it. It would be great if the server would automatically seek the data from metadata sources anidb/tvdb/others and provide not only artwork but plot details/other info/etc.
Feature Request #4
request: Video play queue and play lists
comment: Videos can be played individually just fine, but as would be expected, cannot be queued, or played from a play list.
I understand these features would be a move away from subsonic being predominantly a "music streamer" and becoming instead a "media streamer", but as subsonic is already the best video streamer in my books this seems like a natural progression.