I would totally use Doug Fir for certain furniture applications if it was clear vertical grain, older growth and tight grained. Concerning the Janka hardness of Doug Fir compared to Western Red Cedar (mentioned above), the fir (650-700) is nearly twice as hard as WRC (~350).
Doug fir can be splintery to work with, though. I have worked Doug fir many times during timber framing and you always have to be conscious and careful when cutting joinery and using a chisel aggressively. It can take on a beautiful finish with Tung Oil based stuff, in my opinion. I'm currently building a Roubo workbench using salvaged/orphaned drops from previous timber framing projects and am using Doug fir for the legs and stretchers. I think it will be plenty strong and hard enough for that application.