I currently use nant, ccnet (cruise control), svn, mbunit. I use msbuild to do my sln build just because it was simpler to shell out.
Are there any merits to switch
I think they're relatively comparable both in features and ease of use. Just from being C# based I find msbuild easier to work with than nants, though that's hardly a compelling reason to switch.
What exactly is nant not doing for you? Or are you just hoping there's some cool feature you may be missing out on? :)
One super-nice thing about C# is that if you have the .net framework, you have everything you need to run msbuild. This is fantastic when you are working on large teams / projects and have people/hardware turnover.
Personally I prefer SCons over both of them :)