It is with great pleasure that I can finally declare the infamous, painful, long-standing, never fixed IE memory leak bug fixed! With the release of IE9, I have verified that every leak pattern I'm aware of is fixed. It's been a long-time coming, but I'm starting to feel more confident that IE9 can be reasonably called part of the "modern web" -- the web that is sufficiently powerful to support complex applications, and not just lightly scripted documents.
One caveat: Do be aware that your "standard" pages need to explicitly request "IE9 Standards" mode, using either an HTTP response header or a meta tag like the following:
<meta http-equiv='X-UA-Compatible' content='IE=9'/>
Failure to do so, in addition to giving you all the old crufty bugs and quirks in previous IE versions, will continue to leak memory, presumably because it is using the DLLs from the old rendering engine.
Now perhaps I can finally stop writing about this stupid bug!