Daemon Prince of Chaos

In a nutshell: Pretty much the same big badass from the Chaos Space Marines Codex. The differences are, a few options are incredibly high priced (flight, armor) to get you to buy the Soulgrinder. Yeah I know, I'm being cynical again. Just the way it is, sadly the DP model sold itself a long time ago. ;)

Pros: With all the different marks available and the individual sub abilities each mark grants, this is strangely one of the most configurable units left in 40k. You can make it shooty or assaulty, give it a utility role...just about anything.

Cons: No fleet. The armor and flight upgrades are very very pricey. The lack of fleet makes them very slow or very expensive.

Tactics: Slaanesh gives you Hit & Run and Pavane--don't buy flight, pull enemies towards you then H&R out. Khorne gives you psychic immunity and more CC killy--you'll need armor to survive and flight to get there. Tzeetnch gives you a better invulnerable save and anti-tank shooting, this is a standoff unit, you don't need flight or armor. Nurgle gives you a better toughness and a nasty 2+ re-roll to wound, sadly to really make this unit shine you need flight and armor. The way you run these units really depends entirely on your army build, but those are the basics.

Final word: While very configurable, because of the ridiculous price points of flight and armor, most armies should just go with Soulgrinders instead. They don't have utility like the Daemon Princes do, but they do have a big fear factor. Anyway, there's nothing wrong with Daemon Princes but giving them better survivability and better mobility makes them very pricey. You can however run 3 big DP's and 2 Greater Daemons and you'll have a army people don't like, the 5 MC list. :)