There was recently a topic in the mailing list about continous build and it was suggested to use hydra. There is indeed the possibility to use servers at Delft University of Technologie: http://nixos.org/hydra/
But I recently came across the atlassian website (http://www.atlassian.com/) and they're offering to open source projects a far broader range of tools for software development (including continous building). What could be the benefits and the drawbacks of using such a service?