Right now Warlock feels like a lackluster Mage. Mages got given all the anti-Warlock tools (be prepared to be blown apart by Mages), whilst aside from a 30 second Demon Form (which can still be CC'd) and a circle you have to preemptive put down (not usable while stunned), Warlocks have lost most of their anti-magic defenses as well as remaining as vulnerable as ever to melee.
But the developers don't like/know what to do with Pet classes (hunters + locks lacking pet scaling), nor do they like/know what to do with Dot classes (only partial critting of dots, lack of haste scaling). Burst classes can blow you away; Warlock CC (fear/seduce) is at best an interrupt; magical resistance is almost gone; and melee resistance is a 2 minute Death Coil which Koraa tells us "is fine" (there are other classes which have lower-tier talents to reduce CC effects, not a 51 point talent).
It admits that some of the suggestions might be overpowered. However, many of those that chat on that topic agree that he's created the pizzazz, the zing, that Warlocks have been looking and hoping for from a revamp of the class.
At present Warlock feels almost like nothing really has changed. We don't think Demonic Circle, outside arenas, is going to be that useful as is; nor Shadowflame; nor do we think Warlocks in PvP have much to look forward to.
The emphasis seems to have been on number crunching and PvE balancing for 25-man raids at level 80. Almost everyone who's tested Warlocks so far seems in agreement that PvP viability has gone down the toilet.
At least Guffn has made some innovative suggestions, around which a developer/designer could gain some inspiration. The lamentable state of the Shaman class, however, (3+ years needing a fix) doesn't always give us hope. Still we like some of the suggestions from here. You would love to see a buffed or fixed % version of Soul Depletion come back into the game.)
They made Retribution Paladins viable; and they created a fun new class, the Death Knight, so we think Blizzard can do revamps and do them well. But they need to lose the fear of DOTs, and fear of Pets they have.
We think the main thing from the experience testing the class in play is to highlight some areas where we feel the class could use gameplay improvement. For example, almost every Warlock we know in beta.
We do not think our Warlock class is busted and is going into the ground; it is still a few months until all this is sorted out, we just would like to see some focus put back where it belongs, strengthening the system, and making it fun for everyone. We love our Warlock and love all the things we can do with them, we would hate for us to be the "Enhancement Shaman or Pre-Patch 3.0.1 Retadin" role, easily cc'able and not so much of a foe. We know a lot of this might not make sense, or maybe we are talking a load of crap, but this is how we feel. Every class right now has an edge over one another, take that edge away and you will be left with a blunt object. Come on dev's, don't take our edge, let us have that sneaky ability to somehow manage to come back from the dark abyss of almost dying but having all our dots do something magical. Let us be able to counter a few things, while still be susceptible to other classes. Let us have some fun, but in the process, fun for others.