Well, it looks like Black Knights recieved a slight, 2 point cost reduction per model in the rumors that are our so far for Codex : Dark Angels.
Other than that, they appear almost exactly the same in terms of rules and Wargear, except for the addition of the Ravenwing special rule (i.e. allowed to re-roll failed Jink saves) and the nerfing of the Rad Grenades on the RW Grenade Launcher (no longer reduceds T by -1; instead, causes 2W for each to Wound roll of 6).
Altogther, with the point drop and addition of Ravenwing special rule, I think the Black Knights went up in relative combat power, even in spite of the significant hit due to the nerfing of Rad grenades. First of all, with Skilled Rider and re-rollable jinks, if they choose to give up shooting at full BS, they suddenly have better than Terminator Armor protection in terms of their cover saves (only an 11% chance to fail their Jink saves and they can only be ignored by Ignore Cover weapons, which are significantly rarer than AP2 weapons). Combine this this with their 12″ move, T5, Scout, Hit and Run, and ability to Turboboost and they are easily one of the more versatile units in the game. Additionally, they still have 4 S5 AP- Rending attacks per model on he charge, they still have TLed Plasma Talons on every bike that doesn’t take a RW Grenade Launcher, and they have excellent synergy possibilities with other units.
Some examples of these possibilities are:
-Dark Shroud — The obvious one, but nevertheless excellent. Giving nearby Black Knights Stealth means that they then have a 2+ re-rollable Jink save, which makes them near impossible to kill with non-Ignore Cover shooting. Addtitionally, if they declare an Assault while within 6″ of the Dark Shroud, enemy units cannot fire Overwatch on them… quite a signficant bonus there!
-Allied Biker Sanguinary Priest — With the ability to basically attached an IC Apothecary from allied Blood Angels, this makes the Black Knights even more durable with the addition of FNP and, if properly equipped, some Grav Pistol shooting (to potentially knock a target down to I1, due to the Concussive rule, before the Black Knights charge), an Auspex to reduce enemy cover saves, and/or some Power Weapon attacks from the Sanguinary Priest to supplement the Black Knight Corvus Hammers and Huntmaster’s Power Weapons.
-Dark Angel Rhino Primaris — With the ability to to, once a game, dispatch a Targeting Data Servo-skull to a unit within 12″ in the shooting phase, the Rhino Primaris can allow a squad of Black Knights to fire Snap Shots at full BS for a turn. This means they can Scout and move up turn 1, then Jink to get 3+ (or 2+ with Dark Shroud support) re-rollable cover saves against enemy shooting, and then STILL shooting their Plasma Talons at full BS the next turn, suffering none of the disadvantages of jinking. Finally, the Black Knights can also be used with the Rhino Primaris to engage an enemy Deathstar unit protected by the Invisibility power. Imagine a squad of 10 Black Knights moving with 9″ of an opponent’s Centurionstar with Invisibility successfully cast on it…. using the Targeting Data Skull from the Rhino Primaris, the Black Knights can rapid fire with 20 S7 AP2 shot at BS4 and with re-rolls to hit, getting an average of 17-18 hits — wounding on 2+s, this yields an average of 14-15 AP2 wounds, which means the entire Centurion squad should be wiped out, unless it has some sort of cover or Invul save (and even then, it is possible that they whole Deathstar will be destroyed in a single volley).
Needless to say, I think that Black Knights will feature prominently in Dark Angel list for the upcoming codex, given the buffs they recieved and the synergistic possibilities that are out there for them.