I’ve been keeping an eye on the progress of the R Tools for Visual Studio (RTVS) project. RTVS is an add-in for the Visual Studio program. A preview version of RTVS was announced in March 2016. See https://blogs.msdn.microsoft.com/visualstudio/2016/03/22/introducing-r-tools-for-visual-studio-3/.
It’s too early for me to form an opinion yet. However, on the plus side, VS is an incredibly powerful IDE so RTVS has the potential to be very powerful. On the negative side, one of the things I like about R is its simple environment (I use the built-in Rgui.exe program).
Another thing that comes to mind is possible integration points between the R language and the C# language. Currently R has no good interop story — the usual approach is to transfer information between programs in the two language using text files.
One thing I definitely like about RTVS is that you can easily configure three different R engines: CRAN R (“regular R”), Microsoft Open R (a Microsoft distribution that has improved performance and version dependency features), and Microsoft R Server (a distribution that has libraries for working with huge datasets stored in Azure).