I'm quite prepared to pay for tools that offer a meaningful productivity boost, and while I haven't tried Bud yet, I've had lots of misery with MSBuild and complex builds. I think there is plenty of room in the ms ecosystem for a better build tool, and if it's better enough, I'd be prepared to pay.
I don't think it'd be too hard to make a build tool as much better than msbuild as intellij is better than eclipse.
This whole topic nearly triggered a rant about how badly broken most build is, and how massively it smashes you out of your flow to have an irritating build problem show up. Build problems impact the productivity of every member of your team.