Well xvba-video is certainly needed, otherwise vaapi apps will not work with ati. As soon as the pw protection is removed i will add it to my script for ati cards. Currently you can try it with nvidia and intel. A known limitation of mplayer-vaapi is that OSD is not displayed - I hope this will change soon as it is a no go for many people who want to use subtitles. Also compared to vdpau vaapi is currently more problematic when you try to play unsupported formats as it can not used as generic output plugin. vdpau can be used much easier with a small .mplayer/config file. How this would look like you see there:
This script installs a pure mplayer (maybe the best if you want to report mplayer errors). It does not support vaapi yet. You can use the same configfile with vaapi mplayer and nvidia card as vaapi is mainly just an extra output plugin that does not affect vdpau. I prefer currently nv 190.36 driver for this.
For users without hardware acceleration you can still use multithreaded mplayer. Just give it a go: