NHibernate is (again, imo) arguably as good as or better than EntityFramework, yet (again, in my experience) no one tends to even be aware it exists.
I've seen this as a small part of the larger disappointment I have with "the" .NET community. Despite my love for .NET/C#, I have no love for IIS, web.config files or the broken Debug/Release configuration management in Visual Studio (1). Since I've worked with the .NET web stack, I've gone back to python, ruby and now golang and I missed them and the community (IRC, mailing lists, IRC, forums [that weren't written in 1995], IRC, etc) so, so much.
(1) (for a regular MVC project it's not awful, but for an Azure project it's very inconsistent, hard to control, and easy to screw up which is annoying with 45 minute deploy times, using something other than MVC or EF helps a bit as you can do more in the configuration either in code or XML rather than having to flex opaque VS options)