I notice that "implement a blog" is the new "Hello World" for introducing a web framework.
Blog/Poll are both certainly good examples of common uses of a framework.
I personally did the blog/poll test on a few frameworks I evaluated.
Why use HTML-TEMPLATE?
I've used it before because I've wanted to separate my Html code from my Lisp code. It works well enough. It even automatically updated itself when I changed either my Html or Lisp code.
I did have to bundle all my variables up into a hash table though.
Coming from Python and Genshi templates I found HTML-TEMPLATE to be incredibly ugly. It would appear that YACLML seems to have an implementation of TAL (which came from Zope) that seems a bit closer to Genshi. Otherwise you have a higher chance of generating proper XHTML with CL-WHO than with HTML-TEMPLATE.