I know this is probably a non-programmer way to think of things.
I was thinking about how one part I like about Xenforo is how fast the moving from page to page is when skimming the pages of What's New. you know clicking this stuff ....
It's almost instant. I assume that is from AJAX, non ?
Switching from page to page is much slower in IPB, as well in IPB, the page blanks and then repopulates, which makes it feel slower.
I assume Alerts are AJAX. I assume the "Thanks for reporting" or "Your thread has been posted" message is AJAX.