Zac Bowling has a post about JavaScript 2.0 [ http://zacbowling.com/blog/2006/02/13/just-cuz/ ]
In it he makes a powerful comment "Embedding mono into mozilla might be a solution worth looking into." I've been thinking about this quite a bit lately and I think it is something that both the mozilla and mono teams should pursue immediately. Mozilla has created a great multi-platform infrastructure that's taking the web by storm. However, the low level programming is not main-stream because it's C++ and the high-level XUL+JScript is not powerful enough.
Adding mono into the mix would give XUL a set of compiled languages, multi-platform runtime and a huge set of usable class libraries. This mix would be a great answer to XAML. This would be the ultimate solution for true multiplatform applications that use the web infrastructure (NOT THE BROWSER) sensibly and deliver fast and rich client experience. I am not a huge fan of using the browser for web applications, i see the whole ASP.NET Atlas and AJAX in general as patches that try to make the browser into something it was never meant to do. XUL was a step in the right direction but it needs a lot more support from professional programming languages and environments.