I just upgraded to 12.04. When I press the super key to open the dash, there's a lag of 1-3 seconds before it displays, with no other programs running. (This is similar, but not identical, to the issue described in Dash application search unresponsive at startup about 11.10.) At login time, this lag is up to 10 seconds, and sometimes the dash doesn't respond at all to the super key.
In contrast, the launcher Kupfer immediately responds to its hotkey, in milliseconds, and responds to my typing an application name also in fractions of a second.
Is there a way to load the dash in memory or a RAM disk of some sort to make it more responsive?