The official PCSX2 0.9.9 release is still a work in progress.
What you're seeing are SVN builds of that progress,
and are available for download on the official site at the following link:
http://pcsx2.net/svn.php
Yes-- There is certainly additional performance possible with these builds (like the MTVU hack).
But-- You should understand these are not necessarily 100% stable at this point.
You may encounter a game that previously worked with 0.9.8, but is not currently working in SVNs.
Just keep that in mind if you encounter an issue with a game using an SVN,
and always check the last stable build to see if the problem is there, too.
Other than that, enjoy the great progress being made lately.
mtvu is the greatest thing ever
from 33 fps,I just enabled it and went to 49-50. woohoo! ;p