You should be careful with the HE versions, since the original version is intended for another processor and some things won't work if installed from app manager. Like mplayer - use the OS2006 repo to get it, or directly from here:

http://repository.maemo.org/extras-d...n770_armel.deb

Also be careful what you *update* through app manager - if you replace vital system libs with other intended for another processor, you can render your 770 unbootable and will need a reflash. For instance if you update MicroB (the mozilla browser) through there i believe it will stop working. Mplayer too - only manually. Most things just work out of the box though.