Basically Rogue-like Psionic class, except we already had the Psychic Rogue which is mostly superior to the Lurk with better power access and Backstab dice progression. The Lurk gets a lot more flexibility thanks to its wide access to augments, allowing it to apply crits and backstab damage to undead and constructs, or apply backstab damage without needing to set it up. This is resource intensive and means burning Power Points as well as it lacking good backstab dice without burning pp and multiclassing or taking prestige levels in Assassin. Where as the psionic rogue gets better Backstab dice progression and doesn't need to burn so much PP to bring the pain.
The big reason nobody gives a damn about the Lurk however is that Lurk originated in Complete Psionic, an awful book Psionics fans hate for being designed by people who seemed not to understand the psionics system. Psychic Rogue on the other hand was part of the web series The Mind's Eye which was not only legitimately and completely free, but well loved for supporting a system Wizards of the Coast rarely bothered to support in the books proper.