Incubi

At 22 points, Incubi have been reduced in cost since their previous incarnation. For those 22 points, you a fleet combat specialist with a 3+ armour save, WS and Initiative 5, 2 attacks base, and a power weapon that lets them strike at strength 4. To compare, a Space Marine squad of 5 Vanguard Veterans with power weapons costs 200 points, as does a squad of 5 Space Marine terminators. Ork Burnas are 15 points a model and Striking Scorpions/Howling Banshees 16. Considering Incubi take the armour save from the Scorpions, the power weapon from the Banshees, and add a considerable stat increase to boot, 22 points is an amazingly good price to pay. They've also gained the fleet and power through pain rules. If you can get them into combat, once they've Feel No Pain as well, they're a particularly deadly unit.

The main role Incubi possess is that of a battering ram unit. They're hard enough to take down all but the hardest of combat squads, and all they need to do that is a hero of their own. The high Initiative ensures they strike first, and due to their relatively low points cost, they outnumber the likes of terminators virtually two to one at the same points. In short, they're capable of rolling up a line with ease. They can munch through the likes of tactical marines without pausing for breath, and are equally capable of going hand to Nobs. They may have some difficulty with the likes of swarms, or monstrous creatures, but that's where the upgrades come in(well for swarms at least).

One Incubi can become a klaivex for 15 points. He can be upgraded to have his uber weapon, the demi-klaives for a further 20, and he has two abilities available for purchase on top of that for ten and fifteen points respectively. He can also take an awesome AP3 Flamer for another 15. The problem is, all these upgrades combined equal out at 75 points, more than another three Incubi! Now one of the upgrades, that gives the Klaivex preferred enemy against characters is pretty worthless, with such a high WS(6), he'll be hitting on 3 or 4 plus the whole time anyway. The other upgrades however, all 65 points worth, are good enough to be worth considering taking, however, they strike me as the sort of thing you'd do with leftover points. If you're attaching a hero to the unit anyway, the Klaivex is an unnecessary luxury.

You'll rarely be taking more than 5 or so at a time, as they they work better in small units due to their elite nature. If you have a two units of five instead of one big unit of ten, not only do you have the option of taking Venoms, you have the ability to threaten two sections of your opponents line instead of just one. If both units are on opposing sides of the battlefield, it forces an opponent to make some tough decisions on where to put his uber-combat unit to take them on.

As such, Incubi can be put into two roles in which they excel, small raiding units, or HQ hunting. In both cases, Venoms are the optimal transport, small, and cheap. A unit of 5 Incubi for disruption amongst an opponents force, or a unit of 4+Archon for comprehensive HQ hunting seem to be the most efficient method for deployment.