I’ve compiled the engine from source using Visual Studio Express. It works fine.
What you don’t get is some of the plugins. Unreal has one for running common build operations with command line options straight from VS. There is also “Visual Assist” which is very popular to improve intellisense with UE4, but I haven’t used it (I’m still stuck with Express).
You can also check out BizSpark. Microsoft gives development startups a free MSDN Ultimate subscription for 3 years. That should give you access to Visual Studio Ultimate. I just discovered this myself, and am probably going to apply.
Edit: Ha, had this tab open for a while before replying and it looks like you beat me to the BizSpark info.