Nhibernate. No issues.

To be honest we're shifting to java. Our license fees are well into 7 figures for MS stuff for no gain. This is the first step. Some subsystems are moving from asp.net web forms+mvc to spring, tomcat, hibernate, postgres. Cost savings are huge, staff available are orders of magnitude better and reliability is higher as to be honest, windows has been a piece of shit to manage over the last 10 years.

Fortunately we've got a pretty well designed system so we can move it over piecemeal as and when we update major subsystem features.