Over the past months we made a couple of feature changes in SharpDevelop 3 (currently alpha status). One major change is that we moved NAnt and Mono support from the binary distribution (aka "setup") to the source code distribution. You can find the addins ready to build in the \samples directory:
What was the reasoning behind this decision? For NAnt, we had taken this decision a long time ago because SharpDevelop itself no longer uses NAnt as the primary build solution, and as such, the addin wasn't actively enhanced and tested. But it still is a great tool as well as a good sample for building addins with SharpDevelop.
The decision to "relegate" Mono from production to sample status has been based on multiple factors. For one, we only support basic compilation for Mono, no debugger nor any kind of visual designers (like GTK#). We got lots of support questions regarding these, and the honest answer had to be "we won't support that, sorry". Then in December Miguel announced that MonoDevelop will come to Windows (MonoDevelop is a fork of SharpDevelop), which meant that an IDE would come to Windows that fully supports all the things in Mono we don't have.
That's why we decided to make Mono an addin for people who know how to deal with source code, all the features are still there. And now that it is separate, it also makes a great sample addin because of the deepness of integration with low-level features of SharpDevelop.
To sum it up - we didn't remove anything, we just trimmed the setup to include features that are targeted at the Microsoft .NET platform.