The Kill Team box is exceptionally good value and continues a recent trend, with GW releasing a boxed game containing rules and models for well below the price of buying just the models separately. Some of the other boxes GW has released have only been around for a short time (e.g. Renegade), but they don't always announce if these are limited editions or not. I hope this one stays around for a while.
Kill team games are also quick so are very good for younger players. Those with longer attention spans can easily play 2 or 3 games in an evening, which is great for club leagues.
If you bought the old Kill Team rules from Black Library, you can download the update for free, which is also a welcome gesture.