I experimented a similar problem.
I use gedit to inspect huge SQL dump files (40-50 MB).
With Ubuntu 10.04 (gedit v. 2.30.3, if I rebember well) I got such files opened in few seconds, while with Ubuntu 12.04 (and gedit v. 3.4.1) the operation is terribly slow and impacts the whole system speed and responsiveness.
I experimented a similar problem.
I use gedit to inspect huge SQL dump files (40-50 MB).
With Ubuntu 10.04 (gedit v. 2.30.3, if I rebember well) I got such files opened in few seconds, while with Ubuntu 12.04 (and gedit v. 3.4.1) the operation is terribly slow and impacts the whole system speed and responsiveness.