The latest recommended version of MPlayer for Nokia 770 is mplayer_1.0rc1-maemo.9 right now. Almost all the next builds mostly addressed various N800 related problems and there wasn't much sense to provide updated packages for Nokia 770.

Everybody cared about N800 lately just because it had much more problems than 770 with MPlayer (and with the built-in player before the latest firmware update). Surely, supporting N800 takes time which could be otherwise used for Nokia 770 related improvements, but that is life.

PS. That's offtopic here, but I myself still prefer Nokia 770 design (hard cover) and the ability to hold it firmly with just one hand. I mostly use it for e-books reading on the subway (Nokia 770 really shines for e-books) and sometimes for watching transcoded video. So for my usage pattern, Nokia 770 is clearly better than N800 at the moment (which could be changed with a dramatic N800 video performance improvement later). I'm definitely not going to drop development and support for Nokia 770, at least while my unit is alive and working.