Agreed. We actually gave mono a thumbs down as choice for a recent project because of similar concerns. Xamarin support for the project seems to have slowed as

Agreed. We actually gave mono a thumbs down as choice for a recent project because of similar concerns. Xamarin support for the project seems to have slowed as they have moved into mobile dev tools. As examples there has been no official release of version 3. The last stable version is 2.10. Second there is no indication they will add Web API support, arguably the most important recent ASP.NET addition for those looking to do a REST interface in .Net.