With the Warlock, it's hard to compare them to other strikers. They're more of a Striker/Controller with the way they can throw around status effects and do all sorts of crazy things with their curses. They also tend to focus a lot on single targets, whereas the Sorc has a LOT of multi-target blasts. The problem with those blasts though, is that it's very easy to get allies caught in them and then you can end up applying some of that huge damage potential to them.
Sorcerers, and most of the other strikers too for that matter, don't really seem to have the same ability to just screw over a single opponent like the Warlock can. Plus, while the Sorcerer gets extra damage multiple times per turn, the Warlock can curse every enemy in the encounter and reap huge benefits as the party drops them.
Really, the only big problem with the Warlock is the split stats, but that only really affects you if you let it. It's relatively easy, and should be even easier with Arcane Power out, to pick all of your powers to go with only one of your stats (CHA or CON). If more people would do that, I think that they would find the class working a lot better. Then you can throw in some of the new feats, like the one that lets you use two implements, to add to your damage and general utility, since their implements are both one-handed. All in all, the damage output won't be as sexy as the Sorcerer's, but the Warlock can really mess up some of those Elite and Solo monsters out there a lot better than the Sorcerer can.