Though about this while working on some of our Judith River stuff today:

Can you tell the difference between shed Daspletosaurus, Albertosaurus, and Gorgosaurus teeth?

And if so, how?

You might try asking Phil Currie. He is able to differentiate theropod teeth based on the number and shape of the serrations ("denticulations"). I think the anterior serrations are more diagnostic but you'd be better off asking Phil.

There is a paper in Dinosaur Systematics: Approaches and Perspectives (1990) Ed. by Carpenter and Currie called Theropod teeth from the Judith River Formation of southern Alberta, Canada written by Currie, Kieth Rigby, and Robert Sloan that addresses this very topic. It doesn't really get into specifics between different tyrannosaurid teeth but it might be a good place to start.

Thanks for the reference. Hopefully the serrations are intact enough to make a call.

And while we're on the subject, what do you all think of "Aublysodon". We have 5-6 unserrated theropod premaxillary teeth from one of our sites. From my reading, it seems that this genus is iffy at best.

Well, they may be distinguishable based on a number of factors:
1) Geologic horizon
2) Serration density
3) Enamel microstructure
More to come on this soon.

I'll try to get a photo up ASAP. My camera unfortunately has been damaged in expedition 1 of this field season.