I'll take a crack at a couple comments.  I have been watching the whole AJAX phenomenon as well.  Interestingly enough, a few weeks ago I ran into something somewhere by a bunch of IE developers who were bashing AJAX as being slow and unsafe.  It sounded to me like they just didn't want to have to code for anything non-MS.

Also, I noted your comment about FF being the closest to a W3C compliance.  I just saw something that showed Opera as being more compliant.  Even those were beat by some small user-base browsers that are designed specifically to be compliant (though I'm guessing they lack some features as a result of that).  I'll have to see if I can find one of the sites referenced - it was a pretty cool demonstration of how IE botches up something very simple involving background images.