Although it appears many don't like it, I LOVE it. In terms of class association with classics of literature it has the clearest association with Elric that I've seen in any RPG outside the eponymous one, and is all the better for it.
I love the way they have characterised the class, giving more detail about the way in which someone becomes a warlock, and in a way which drips both RP potential and campaign building potential.
I love the way that they appear to have ditched fiddly curses (I've said before that marks/curses/quarrys etc was one of the complications to melee that I felt they had got really wrong, as it hampered and confused melee badly. Others love it, but it really helped drive me away from 4e).
I don't mind them largely losing encounter powers (perhaps just having some generic ones based on their pact?) and I like the existence of daily powers to keep with the essentials vibe that daily powers are magic spellcasting.
All in all it is one more reason to purchase the next book, dang it!
Cheers