https://bugs.freedesktop.org/show_bug.cgi?id=34495
--- Comment #17 from Pierre-Eric Pelloux-Prayer pelloux@gmail.com 2011-06-27 07:38:42 PDT --- The massive slowdown observed when selecting an object seems to come from Blender's usage of GL_SELECT rendering mode, which AFAIK is software-rendering.
Hardware support for GL_SELECT in Mesa should solve the problem, but I'm not sure this is going to happen.