You can find out more about the roundup, and sign up here. We're also holding a Flex Jam the 3 days before the Roundup.

Fan is an interesting language because it attempts to pick and choose among the best features of both Java and C# and add features missing in both. It runs on both the Java VM and the .NET CLR.

Although it provides a syntax that will be familiar to both Java and C# programmers, it attempts to remove much of the cruft from both languages -- it doesn't go as far as becoming curly-brace free (too abrupt for programmers from C-based languages), but it does make a lot of design choices in the name of improvement. I rather like that the language designer(s) has a strong opinion on some things, for example:

Checked Exceptions: checked exceptions are evil syntax salt. Checked exceptions don't scale, don't version, and don't allow composable systems - all the reasons why Anders Hejlsberg didn't include checked exceptions in C#.

There's a rather compelling design document here that's worth reading -- it gives you a strong sense that the author(s) set out to solve all the problems that they encounter.

We have moved into the age of the virtual machine, so language designers can now create new, experimental languages that can be used for real projects. Because they run on VM's that do most of the low-level work, these experimental languages can rapidly become practical.