I've used nHibernate for ~7 years at this point and I push it whenever I can. One of the big issues it faces is that there's no documentation equivalent to MSDN. Even if the MSDN documentation is useless (which it frequently is, with things like "The IsClosed property indicates if the object is closed.") it still "looks professional."

I think you can do amazing things with the .NET platform, but it mostly requires a certain amount of, for lack of a better term, fearlessness when it comes to what you build your system on. Using anything that isn't blessed is often an uphill battle where you are met with suspicion and derision.