Note: I've checked the continuous-integration tag here and also the automation tag. (Other questions, e.g.: remote build experiebnce?.) (I've also found one question on SO for an example of a more specific question.)
Anyways, let's get a bit of context here:
Wikipedia lists as Build Automation Software a lot of tools, but those that qualify as a "build server" seem to be listed under Continuous Integration Tools. However, CI only is a part of what a centralized build server needs to do.
The software tools available seem to be slightly skewed towards Java (and .NET), but what about Build Automating Servers building (continuously or nightly or on request) & testing & packaging native C++ apps? What is your experience here? How do you find the scripting? Does it scale? Is it easy to administer? Does it have a good Web interface? Etc.