I finally sat down & played Lair of the Shadow Broker. I'd rate it with a 10/10 if not for a crash during a cutscene, forcing me to re-do a bossfight. Oh, and that car "chase" was retarded. The Sentinel class again proved its superiority; coming with Liara's Singularity & Warp and Legion's drone & head-popping all the filler combat was over very, very quickly.
I do think, though, that it should've been part of the vanilla game. The dossiers alone, for instance, clear up a few glaring plotholes in ME2.