This deal really cant be beat. Although the fourth was dysmisal, the first one was classic, the second excellent, and the third interesting.
While not cram packed with extras (and I do wish the omen legacy dvd had been included!) - the first is a special edition with a 45 minute documentary, 666:Curse or coincidence featurette, Jerry Goldsmith discussing his score, and more. The second and third have trailers and full length audio commentaries. The fourth has nothing except trailers for the others (which doesn't make much sense since there is a trailer for the fourth on the omen legacy disc) -- but overall this is a steal.