OK, but in that case, what you really mean is a web app built for browsers that haven't even been released yet. I'm sure for some people/projects that is a serious issue, but I think your characterisation is a little unfair.
> But there are also a number of things like rounded corners, transparency, and event handling that are irksome. Thank God for jQuery.
Sure, those are annoying, but as you point out, solutions are easy to come by.
> IE8 and below were simply too feature-poor to even begin to run it (start with missing canvas, and work from there).
http://excanvas.sourceforge.net/
You're welcome. :-)
> When I read your last sentence, though, I see "the problem is with everyone else, not IE".
Not everyone else, just a small list of specific groups whose specific rapid-release policies keep moving the goalposts. Coincidentally, those groups hold much of the market share not held by IE today, but the point isn't that IE is somehow superior to everyone else, just that I don't like the policy those particular groups have adopted for the reasons I have been giving in this discussion.