The one thing that made me switch was the many different text files I was editing. vim makes editing text files very easy and there almost always a syntax file for the type of file you are editing.
I use vim so that even though I may be editing C++, Ruby, YAML, JavaScript, Python, HTML, and CoffeeScript in the same day, I can still use the same editor and shortcuts across all the different types of text files. Also, vim is always one of the first editors to get syntax files for a new language.
If you only do ASP all day, VS is worth sticking with.
I use vim so that even though I may be editing C++, Ruby, YAML, JavaScript, Python, HTML, and CoffeeScript in the same day, I can still use the same editor and shortcuts across all the different types of text files. Also, vim is always one of the first editors to get syntax files for a new language.
If you only do ASP all day, VS is worth sticking with.