Nice article and I agree with Ross. The discussion with people "missing" SIS functionality tends to be fed by gutfeeling. Nobody can size this properly with so many variables in a living system with a dynamic population. The argument of recovery may be valid, but do not forget that the best practice regarding database sizes versus recovery times isn't related to type nor number of attachments. IMHO, you *may* have benefited from SIS in the past, but you *will* benefit from storage changes in 2010.
I've jotted down my thoughts on SIS here (shameless self-plug)
http://eightwone.wordpress.com/2009/11/25/exchange-2010-database-compression/
Microsoft
