Better code navigation in F#
Bring over the code navigation features found in the VB.NET/C# Visual Studio experience, such as Find All References and Call Hierarchy
Another helpful addition would be dropdowns for jumping to types and (maybe) functions/methods similar to those that exist for C# code.
I am surprised this hasn't received more votes. Even more important to me is that "Go To Definition" (F12 or control-click) currently doesn't work from F# into other assemblies written in other .NET languages. This makes the F# development experience extremely poor in a multi-language situation. For anyone trying to introduce F# projects into existing solutions without rewriting the whole codebase in F#, this is a pretty big deal.