I just finished building a fairly complex Ramsey kit and was impressed by their level of detail. They even explain the circuit theory where it's important to understand how the thing works. While it lacks the professional fit and finish of Heathkit, it's a good first-kit experience for adults, and they have a huge variety of applications.
I have also built Ten-Tec and Elecraft kits. I wasn't too impressed with Ten-Tec - the circuit board had a fabrication error that I had to troubleshoot and figure out myself. Elecraft seems to be the new gold standard in ham kits. Their manuals are excellent and the equipment is top-notch. (Can't wait to get my hands on a K3)
"I've seen it. It's rubbish." -- Marvin the Paranoid Android