UnityVS is now a product of Microsoft, as Microsoft Acquired SyntaxTree. This means that you can use Visual Studio to develop Unity Apps, Games, for free.
Some cool features include:
Project Explorer right inside VS, no need to jump over to Unity while coding
Integrated Error List window: No need to jump back to Unity to see the console to see where is wrong in code. Cool!
Code template and snippet generation:
Amazing tools and free! Previously shareware! Enjoy!