Damn, hopefully YDKJ goes 50% off like Metro. Would definitely pick that up as well. Maybe the Jack Packs as well. How good are those?
The Jack Packs are definitely up to the quality of the on-disk episodes, writing-wise, they offer a lot of bang for your buck, and they have some pretty quick and satisfying achievements, if you're into that kind of thing.
One thing to keep in mind, however, is that Jack Pack 2 is made up of questions from the web YDKJ that Jellyvision made a few years back (not the current Facebook game, but the beta thing that predated both that version and the Xbox/PS3 one). So if you played that older Jack, you might have played a few of those questions. Packs 1, 3, and 4 are all new content, though.