I've uploaded SMPlayer version 0.6.0 RC1 to Debian unstable and got it synced to Ubuntu Hardy.

Gutsy has 0.5.62 in backports. To the end user, the main difference between the repository packages and upstream ones is that the former are split into smplayer and smplayer-translations.

Also, if any Debian developers happen to be reading this, I need sponsorship for smplayer-themes. It's listed in the Recommends section of smplayer, but not currently in Debian. (It is in Ubuntu, however.) It can be found on mentors.debian.net here.