In C# at least, MSVS intellisense displays information about functions and their parameters in the summary tags. There is also a return tag for description of the return value.
This page talks about viewing the function signature and parameters http://msdn.microsoft.com/en-us/library/25cey46e(v=VS.90).aspx but what about the return value description?
Currently, I right click on the function and “go to definition” but i hope it can display inline as a tooltip.
If you are using Resharper, try CTRL+Shift+F1 (VS-Key Scheme) or CTRL+Q (ReSharper Key Scheme), it displays Quick documentation, inclusive return type. See http://www.jetbrains.com/resharper/features/coding_assistance.html#Quick_Documentation