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'm actually still trying to figure this question out myself, but there is one big bonus for MSBuild here: using the same build file for local continuous integration by calling msbuild.exe directly, while also being able to use VSTS's server-side continuous integration with the same build file (albeit most likely different properties/settings).
i.e. as compared to TeamCity's support for MSBuild scripts, VSTS only supports MSBuild scripts! I've hacked around this in the past by exec'ing NAnt from MSBuild; I've seen others recommend this practice as well as the reverse, but it just seems kludgey to me, so I try not to do it if I can avoid it. So, when you're using "the full Microsoft stack" (VSTS and TFS), I'd suggest just sticking with MSBuild scripts.