These are my BRD titles, I don't even have a player anymore:
Goodfellas: Amazing transfer
Total Recall: Shit transfer
Layer Cake: Amazing transfer
Akira: Like orgasming non-stop for 125 minutes
Outside of that the only movie I checked out that I really felt compelled to buy was The Fifth Element, since the transfer made it look like a brand new movie. Oh and any Pixar film I'd say is worth getting on Blu-Ray.
EDIT: I think one place the whole Blu-Ray marketing fucked up is how every player including the PS3 comes with a kick-ass upscaler. So even though DVD video still has compression artifacts, it doesn't look like utter shit in comparison like it would sans the upscaling.