In the last codex this area, well just sucked ass. Now, we have something that makes us proud and perhaps a very viable option for army building when it comes to Chaos.
Chaos Bikers: Price per pound, simply a great choice. Add the mark of Nurgle and some melta or plasma guns and a possible character that is compatible with the unit and have fun! Go on, waste your ammo on this unit, the rest of the army is going to pound you and if you don't pay for it later.
Chaos Spawn: Here was another really bad unit that now has some options to it. To me this is a cheap bullet magnet and can draw attention away from the army without paying a high cost. Ignore it? Well, may suck for you later.
Raptors: Chaos has useful dump troopers again and cheaper (perhaps slightly better) than the marine version. Depending on options this unit could be a serious threat to your opponent with proper scenery and screening by transport vehicles.
Warp Talons: They are very expensive, but if you apply them correctly they can garner a great value on the field. Then again, they can also be a serious liability if you are not careful.
Heldrake: To me the most popular of the choices, load them with a baleflamer and enjoy roasting marines over an open fire. A flying hellhound marine killer is the only way to sum this up.....oh an you can still strike flyers in the air as you pass over...a two for one value. Please leave the Hades Autocannon at home.