I just came accross an interesting article that shows another technique for injecting some dynamic content into a page or control that uses outputcache
http://www.dotnetbips.com/articles/displayarticle.aspx?id=516
The Substitution control, I wasn't aware of this control at all, though now I see it is even listed in the book I have, just didn't notice it.
I may have to do some more experimenting with this and see if I can overcome the issues of output caching using this.
Joe