Here is chart for opening task page process on demo site:
http://wstaw.org/m/2011/07/11/plasma-desktopNT3057.jpg - 2.62 seconds.
It is not slow, because demo have not many projects and tasks.
And here is chart for opening task in our system:
http://wstaw.org/m/2011/07/11/fo1.jpg - 5.48 seconds.
System have about 100 projects and 4000 tasks, 100 documents, 200 notes, 10 tags.
So, as you see, 1830 ms (milliseconds) spend to generate first page (index.php) and other - for JS and AJAX requests:
Total JS: 652 ms
Total AJAX: 4267 ms (4 seconds!)
Slowest JS: 145 ms - load language translate strings
Slowest AJAX: 2239 ms - //?&ajax=true&active_project=23&c=task&a=view_task&id=483&utz=4¤t=overview-panel&_dc=1310385308612 (load current task with id from url)
Next slowest AJAX: 957ms - load tags with number counts.
Task page ajax load process started only after 3.13 seconds after page load started.
So, if we start load task at first page load (without ajax), we will render page (to see the task) with the 2.5 seconds instead of 5.48 - more than 2 times speedup.
To load CSS we spend 595 ms, to JS - 635 ms, so combining and compressing js and css will increase page load time by 0.2-0.5 second maximum (because after this we must spend time to pase js and css anyway).
Tests are done with Chrome browser, so every user can repeat it in his system and detect slowest parts of page rendering process.