Just a small addition for:

"I've heard various answers, but the answer given by one of the panelists, that there hasn't been a widespread adoption of RAC, so why should Microsoft invest in it, is one that I wasn't expecting. It does make sense as SQL Server exists to make money, not necessarily be the best product. If there isn't a large demand, then why do it? "

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Gartner just published an article about that here:

http://mediaproducts.gartner.com/reprints/oracle/article61/article61.html

And BTW 3 out of 3 our recently developed apps (I'm working in a development company mostly developing custom Oracle apps) all were deployed on RAC, one with Enterprise Edition, 2 with Standard Edition. However for SE there is limit 4 CPUs for all cluster so usually it means 2 boxes with 2 CPUs. But the advantage is RAC with SE if for free 🙂