The "A" in AJAX is important. Don't design an AJAX user interface thinking in terms of synchronized calls to servers. :P Bad things will happen when you actually connect your UI to that server. :P I learned this at work today. Apparently this is a fairly common problem for people writing AJAX code for the first time. Luckily, it didn't take long to fix.
On a related, the user interface I'm writing at work is now driving part of the backed. I am satisfied. :)