Phil - I took the easy way out and bought a good incubator. Had read too many horror stories about cheap incubators, and had a good job at the time. If I was going to go the cheaper route, I think I'd try to make a coolerbator as a project, or at least buy a Genesis Hovabator - I've heard good things about the 1588.
At least Babs will be home to fuss with it and watch for temperature spikes. Hope she has a good hatch.