Any build automation is better than no build automation :-)
Personally, I prefer daily builds - that way if the build doesn't work then everyone is around to get it fixed.
In fact, if at all possible then Continuous Integration builds are the way to go (i.e. a build on every check-in) as that minimizes the amount of change between a build and so makes it easy to tell who broke the build and also easy to fix the build.
