Hi Folks,
I just installed D7 and even if it looks quite nice, unfortunately it is very very slow. I installed it on the same server, running from the same DB, where I have a D6 test-system running (only D7 having 'drupal7_' as table-prefix), and the "respondiness" of D7 while travelling through the new administration-structures is really annoyingly slow.
On the D6 system, activating modules, adding translations etc. is clicking on "Save" and after at most a few eyeblinks, the system is ready.
On D7 it sometimes runs into Server-Timeouts (browser not loading anything anymore, overlay-content not progressing anymore) but at least every click to a different administrative link takes several seconds (in double-figures). After disabling the "Overlay" module it got a little better, but still is quite too slow to be appropriate for endusers (customers).
Just as an example: just clicking on "configuration" takes 11 seconds to show the configuration page in D7. In the D6 system (same server, same db) I didn't even reach the "two" while counting the seconds.
Server is Apache, MySQL is 5.0.91, PHP is 5.2.14. My System is a Dualcore with 3,2 GHz, running WinXP and D7 is slow in every Browser (Opera, Firefox, Chrome, Safari, IE), so the problem seems not to be related to slow JS on my System/Browsers.