Hi,
I'm running 1.50 (7886) on OS X (10.5.6).
The contextual menu command to Remove Torrent File... doesn't seem to work once seeding is complete. If downloading, seeding, or paused manually during seeding/download, the item works as expected. Torrents are removed from the list in Transmission and the actual files moved to the trash.
If seeding is complete (per the Preferences>Transfers>Management pane), then selecting the contextual menu item removes the torrent from the active list but does not actually move the torrent file to the trash. To be clear, the torrent is paused when this occurs, but it's paused automatically when seeding completes -- I have not paused it manually.
A small nit, but there you have it.
Oh and it should be said: overall Transmission is fantastic. Keep up the good work.