Comment 49 for bug 379157

From what I have seen from other users, there hasn't been a whole lot
of performance change between 2.4.1 and 2.7.1. Many users report
significant improvement for 2.7.99.1 which is in Karmic now. It will
probably be 2.7.8 by the time Karmic is out, and hopefully it will be
with a solution to your problem. So I would suggest that you keep the
package that is working for you at the moment.

Now, upstream will have to figure out if the best way to solve this
problem is to outright revert the problematic patch or do something
different. You will probably be asked to test another patch soon, but
it may take a little while. You may take a look this bug (which is
similar except that a VGA was sometimes detected when it wasn't there)
for how things may proceed:
https://bugs.freedesktop.org/show_bug.cgi?id=20463
Hopefully, it won't take as long, though.