The notifications page shows warnings if your site is not secure. I noticed a forum post recently by somebody who had been complaining about poor performance and where the solution was to turn off theme designer mode...

In this thread, 3 people said they had experienced this:

http://moodle.org/mod/forum/discuss.php?d=194581

To reduce perception of Moodle 2 performance being even worse than the actual performance, I suggest that the notifications page should warn if:

• theme designer mode is turned on
• javascript cacheing is turned off
• debugging is set to 'developer' mode. (Other settings are used in production, here at least, where we want to catch warnings...)

The basic category should be, settings that are inappropriate for live sites. It could be a box as follows:

The settings on this site are not appropriate for a live Moodle system:

• Theme designer mode is turned on. This makes the system much slower. Change
• Javascript caching is turned off. This makes the system much slower. Change

(links just go to the relevant settings pages...)

Not offering to develop this, sorry, just passing it on as an idea