Hi Simon,
Thanks largely to Ian Lynagh, GHC now has a BuildBot infrastructure to automate nightly builds on multiple platforms. This replaces the old set of shell scripts that we used to run nightly builds; now adding new clients to the setup is relatively easy, instructions are here:
Good news! Do you have any idea of how much time a build might take roughly? As a second point, the Yhc team do a variety of builds - some from clean, some from fullclean, some from delete the directory and a completely fresh darcs pull etc. We've found that can help catch things like interface changes, dependancies etc earlier. If you have (or can find) too many Windows/Linux machines etc that might be worth doing - and is pretty easy with buildbot. Thanks Neil