Currently F# IDE integration into visual studio does not have any refactoring support. It would be nice to at the very least be able to handle renaming.

It would be a tough blow for F# adoption to not provide 'Compiler as a service' when VB and C# does.

Improve F# project model (at least, add directions support). Maybe some extension to the language itself would be pretty good: #require "filename" to indicate that filename must be compiled before current file.

Right now there is a big lack in the async-workflow if you compare it with C#/VB.nets implementation: you just cannot wait one-of-many results and there is no good timeout-support. You allways have to switch back into the Task-world.
Tomas Petricek had some great-ideas (see here: http://tomasp.net/blog/fsharp-variations-joinads.aspx) - I had hoped to see some of this in the new releases but alas no love for us poor pure functional lovers.

Provide the option of having infix notation on functions rather than just symbolic operators

Compilation in F# awfully slow. Please improve this!

It's a big annoyance to not have auto completion there. C# Interactive from Roslyn supports it, and even the Immediate pane of C# and VB also have it

Bring over the code navigation features found in the VB.NET/C# Visual Studio experience, such as Find All References and Call Hierarchy

It would be great if you could provide some parameters to a module, even if it was just at compile time. Something like:

open Module1(p = 100)

This would make a lot of use cases much simpler to deal with while letting the code keep it's functional feel. This is especially true for math related stuff.

Although FP style is Unit Test ready code there is no support in VS for Unit Test feature in F#.

This would allow alphabetically sorted items in the solution explorer, and support for folders in F# projects.

Currently, the only way to organize large F# projects is to (artificially) break them down into smaller projects.

The codeplex project "fsprojectextender" is a proof of concept.

It would be great to define mathematical operators (e.g. ∀, ∑, ∩) in F#, and be able to use other Unicode symbols (such as arrows) in operators as well. So instead of saying

let inline (!++) xs = xs |> Seq.sum

you could say

let inline (~∑) xs = xs |> Seq.sum

Writing "∑myList" is much, much easier on the eyes and brain than trying to figure out what "!++myList" does.

I think there must still be room for improvement in the way the IL from F# is optimized. I'd value that far above the addition of any specific feature. I'd like to stop seeing my lovely idiomatic code get more and more imperative-looking as I work on performance.

Similarly to what was done to the compiler, so people can improve the IntelliSense support, add refactorings, etc., instead of asking for those features here

It would be nice to have break, continue and do-while loops build into the language. It would ease porting existing imperative code to F# or just code fine metal tuning.

I'd like to be able to compose code at run time using F# quotations, which is now possible only with F# PowerPack

For types that are never to escape to the external API it would be awesome to contain them inside of other types. Less cluttered.

more and better floating point optimizations around SSE4, AVX etc

why this is a crucial feature for high performance programming --
either do it on x86 platform or support CUDA ..,. just to be competitive.

Is it many/multi-core CPU-GPU or GPU-CPU?

Please allow to declare and properly override protected members

Create collapsible outlines around functions, type declarations, and workflows at minimum, perhaps around more fine-grained constructs as well. Allow mouse-less collapse and expansion with Ctrl+M key.