Amlogic is known around the XBMC/Kodi forums for their excellent OSS VPU drivers and boxes using this chipset are usually among the most recommended.

This new chipset (S805) should also be able to support H.265 videos, the first patches for it have already appeared on the mailing list.

I can't comment on VDPAU support but for Kodi this board should be pretty awesome :)