InfoQ has been running a CI server survey for more than a month now, and here is the current result:
Jenkins has gotten more than 70% of the votes, once again proving the wide adoption among developers. If you are one of those who picked Cruise Control into the "considering" section, I'd encourage you to look around a bit more.
You can still vote from their website or leave comments if you want.
By the way, the design of two axes make no sense to me; for example, I'd order the adoption axis to "considering -> migrating to -> using now -> moving away from", and the circle seems to imply two axes are somehow interchangeable, when it should probably be just in a checkerboard to indicate those are independent axes.