At the time the Cortex Plus Hackers' Guide had come out there were three major published games using Cortex Plus; Smallville, Leverage, Marvel Heroic Roleplaying - but the license for both Smallville and Marvel Heroic expired at the same time (Firefly has now been added to the ranks). The Cortex Plus Hackers guide presents generic rules for all three games, plus handfuls of hacks for each of them, showing how to adapt each of the three games to various settings.
The system (or more accurately the family of systems) is fast, light and incredibly evocative as long as the GM is good at thinking under pressure and coming up with random complications at a pacing set by the system. The biggest weakness of the system (or rather systems) are that they are incredibly swingy.
[4 of 5 Stars!]