I am playing with Shoes. I doubt anyone would do any difficult app with this, but for simple GUI hacks, it seemed pretty okay. I have several problems. And the whole idea of doing it as a domain specific language and not as a Ruby gems has some pluses, but if it was just a simple standard Ruby gem/framework as rails, it would help much more. I also have the same problem as one user when using HTTPS.
Anyways, Nobody knows shoes is a pretty interesting book to read (it’s a 40-page PDF with very little text), I must say I never seen a GUI framework tutorial presented in such a way. Worth reading even if you don’t intend to program in Shoes.