Below is the complete (but short) list of things that are not supported yet or are known problems in the current build of X#.
•Some parser errors need improvements, compiler errors may be cryptic every now and then
•Sometimes you may see a "Include file not found" error, where the file DOES exist. This seems to be a side effect of the codepage that was used to save the include files.
When you save the file as UTF8 (File Advanced Save Options in Visual Studio) then this problem almost always disappears.
•New features in the Debugger, such as a window for Globals and RDD Workareas
•Query Optimization (Rushmore) is not supported yet
•Some runtime functions are not supported yet.