I already had the half-life anthology pack (it was the first thing I ever got on steam, I got it for free by entering the cd key of my original half-life disk) but bought the valve-complete pack last Christmas because it was cheaper to buy all the games I already had in order to get CSS, HL2EP2, DODS, TF2, Portal and L4D then to buy them individually or through some other packs.
What really made me upset is that I couldn't give all the hl1 games away as gifts despite having two copies of them.