MSBuild vs. NAnt

Correct me if I'm wrong but isn't MSBuild a knock off of NAnt or any other derivative of Ant?

Is the only reason MS created such a build tool is so that internal MS employees could use it? Do their employee contracts prohibit them from using Open Source tools? That's my speculation. Please correct me if I'm wrong.

It's not a problem if I'm right - but why not just use it internally at MS? Why make it public for everybody's use. We already have a decent tool and we get the source code to boot - not to mention community support.

I didn't get a chance to go to the MS Build presentation (TLS347) so I apologize in advance if I'm just not getting it. I have looked at the slides but there isn't much there - nothing that I don't see in NAnt.

I'm really looking for the killer reason not to use NAnt and switch to MSBuild. Maybe the answer is this..

MSBuild will be the core build engine underneath Visual Studio and share project file formats with VS.NET. Certainly this has caused me some grief with NAnt in the past, mostly with VB.NET since slingshot (the last time I looked) only converted csproj files to build files and not vbproj. So I think the most important thing about MSBuild is not MSBuild itself but that the C# and VB.NET teams will have to (or already have) collaborated on a unified .proj file format. Hopefully the NAnt contributors will write an XslTransform. As an aside I hear that this level of integration won't be available for C++ developers. Now getting three teams to talk to each other - that's just impossible. I bet that the .proj file format changes again when the C++ team gets around to supporting MSBuild.

In addition to the VS.NET integration, there seems to be only 1 other significant difference between NAnt and MSBuild. MSBuild includes some kind of “full inner-task dependency“ that is supposed to allow for incremental builds. While I might care about this for an IDE experience (slightly) it's less important from a nightly build scenario - IMHO.