The Ranco is a good dependable t-stat if you want an on/off t-stat. We have several of them in service along with some Johnson A419s. I prefer the Johnsons over the Rancos, because the Johnson has a few extra features.

I prefer proportional t-stats and will eventually have all of my racks set up with proportional t-stats with on/off t-stats backing them up.

For incubation we use proportional t-stats with on/off back up.