It's got Genesis of the Daleks, Destiny of the Daleks, Resurrection of the Daleks, Revelation of the Daleks, and the Remembrance of the Daleks Special Edition, with previous effects mistakes fixed, a couple of new documentaries, and new 5,1 sound mix. Apparently early pressings of this had a brand new sound fault, but those have since been fixed.
It also has 8 Davros audio plays, one written for the collection. The titles are - Davros; The Juggernauts; Terror Firma; I, Davros - Innocence; I, Davros - Purity; I, Davros - Corruption; I, Davros - Guilt; and The Davros Mission.
On one hand, it's kind of annoying that they've released this set. On the other, I figure when I'm eventually left with one, I'll sell my copies of Resurrection, Revelation, and Remembrance second hand.
For those who already have most of the stories and don't want the collection, Destiny of the Daleks is getting a release too.