The slowdown is in the cape01.tpw file, which is included with all the templates.
If you are in the habit of using the local extension to declare your objects (rather than just in hand-code) then you'll see it slowed down.
I have released build 3.66 of StringTheory to include a new Cape01 which solves the problem. So if you install that, and restart the IDE, the issue should go away. The upgrade of Cape01 will permeate through other releases as they are updated.
Cheers
Bruce