Thank you for the answer, Don! Very interesting!
Though, seems, you have not answered on the question about IE. It is the second post in this thread just after your initial post. It has 3 vote up, so, probably, it is very important A bit kidding. Generally, the answer "No" is also acceptable. Eventually, you are not Gods to make IE better
Once I faced a performance issue with IE7 and IE8. In other browsers including IE9 it was OK. It turned out that the buttons caused it due to the fact that they were rendered as HTML table elements in IE7 and IE8 (as it was in ExtJS 3). It took too much time for relaying out. But in others it is rendered just (almost) as a div. (it is really cool, by the way). And relaying out occurs instantly... Hmm, I just discovered that now it renders the same way in IE7 and IE8. Cool, thanks!