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 switching my whole build script to MSBuild? I need to be able to run tests, watir style tests, xcopy deploy. Is this easier?
Update: Any compelling features that would cause me to shift from nant to msbuild?
I like MSBuild. One reason is that .csproj files are msbuild files, and building in VS is just like building at the command line. Another reason is the good support from TeamCity which is the CI server I've been using. If you start using MSBuild, and you want to do more custom things in your build process, get the MSBuild Community Tasks. They give you a bunch of nice extra tasks. I haven't used NAnt for several years now, and I haven't regretted it.
Also, as Ruben mentions, there are the SDC Tasks tasks on CodePlex.
For even more fun, there is the MSBuild Extension Pack on CodePlex, which includes a twitter task.
Nant has more features out of the box, but MSBuild has a much better fundamental structure (item metadata rocks) which makes it much easier to build reusable MSBuild scripts.
MSBuild takes a while to understand, but once you do it's very nice.
Learning materials: