Just had a rather nice game as Warlock. We had troll warlord, me, Zeus, naga, and visage.
We only got our full combo off once, but when we did it was hilarious. Naga ultied, and me and zeus moved into position. After the sleep wore off, I fatal bonded all 5 of them, and then me+zeus threw our (upgraded) ultis into the ring at the same time.
Boom, 1200 magic damage to each of them. 3 died instantly, their huskar and lifestealer died moments later.
A few games earlier the opposite thing happened to me, I was Zeus with a Warlock. Three of them ganked me at half health solo mid, Warlock ported in, fatal bonded and ultied. My last second ulti got me a triple kill, taking them all down from about half health to 0.
Man, I love warlock. Fatal bonding someone else's AOE damage ulti and increasing the damage by 80/100% is just so great.
Errr.... That post seems to have gotten away from me somehow.
To add a point into the rambling mess that this post is: Warlock is amazingly OP right now. He isn't the most fun hero by any means, but he is the most powerful, at 58% win chance (although only 34th most played).
Q (Fatal Bonds): Sweet Jesus, 220 pure damage at level 1, with a long cast range as well as being able to use creeps to cast it farther. Not only that, but with your mana you can basically force a enemy out of lane (even if he has heals). And that's overlooking the teamfight potential of having all damage anyone on your team does to a enemy do 80% to the rest of the team.
W (Shadow Word): Meh, a heal is always nice, and the DOT can kill enemies. Not really particularly good though.
E (Upheaval): Very hard to get working properly. Pretty good if you somehow manage it though.
R (GolemGolemGolem): Pretty much the best ulti in the game. It has a 1 second huge AOE stun that goes through magic resist. It deals (slight) AOE damage. You can cast it at a very good range, unlike pretty much every single other AOE ulti. And if that wasn't enough, it summons a unit that for the first 30 minutes of the game is equivalent to a tanky hero, a super pusher, and a carry all in one. It can't actually catch a fleeing hero, but there isn't really any hero that can do anything BUT run from it except a lategame carry. And best of all, there is absolutely no way that it can screw your team over. And even if you somehow completely miss all of them with it, it is still a pretty decent unit to take into teamfights.