The framework is similar in spirit to UCW and Seaside. It is heavily based on widgets. I probably would have ended up using Seaside if Smalltalk supported multiple method dispatch and didn't force me out of Emacs. I didn't use UCW because of a serious attack of a "Not Invented Here" syndrome.
I did not yet implement modal requests. When I do I will likely not use continuations. I have a pretty good idea on how to achieve modal programming style with coroutines.
I make very heavy use of closures and multiple dispatch. Some parts of the framework also put more esoteric features of CLOS and MOP to the test. I use introspection heavily to generate HTML - I couldn't stand using template engines anymore so I wrote code that does the dirty work for me. Macros are put to very heavy use via Edi Weitz's excellent CL-WHO. I suspect I'll use them heavily to implement coroutines.