Is anyone familiar with the sIFR technique and thusly, it's implications on SEO?

I am doing some research for a client, and everything I see indicates that sIFR is SEO friendly. But when I start hearing about image replacement, I get cautious.

For more info on sIFR, here are some links:
http://www.mezzoblue.com/archives/2004/10/26/sifr/
http://www.wizardworks.ca/articles/sifr-point-of-view.asp