It's actually at a Safeway store nearby (B20) and is the same price (or a bit less) than diesel at other locations. My wife shops at Safeway and she gets 10% off on gas/diesel purchases.
Bio-diesel has a higher cetane, but slightly lower BTU content than regular diesel. It's also a much better solvent...if you switch over, make sure you change the fuel filter/water separator more frequently the 1st few tanks/months. It will dissolve any varnish/crud in the fuel system.
My Powerstroke likes it...it seems to run a lot smoother and less "rattle" when cold. I just got emissions done, the soot level was <3%...the std in AZ is 35%. The stuff burns very clean and that helps oil to last longer (less soot). It does get a tiny bit less mileage (15.7 MPG vs 16) than regular diesel due to the lower energy content. I can live with that.