The Avatar of Khaine was the first unit that I really ever loved for its awesomeness. The last Eldar Codex was the first one that I actually properly started getting into and after getting some Guardians and the Battleforce the Avatar was next, and whilst everything around him died he was a bedrock on which I could rely to kick the crap out of stuff.
In the new Codex, he keeps his badass statline, with a couple of improvements. As well as being WS10 he is now also BS10, Strength and Toughness remain unchanged at 6 whilst Initiative is buffed to 10, Wounds to 5 and attacks also to 5. However, there are a couple of negative changes here.
Firstly, he loses his 4+ Invulnerable save, dropping down to 5+ for being a Daemon. This offsets the +1 Wound a little as he only has a 3+ armour save. However, he has got a little quicker. Not only does he have the Battle Focus special rule, meaning that he can run and shoot, but he also has Fleet for a more reliable run or charge.
Closing out the special rules are a couple of little abilities that he has. Starting with the lesser, the Avatar is immune to Pyromancy spells, Melta, Soul Blaze, and Flamer Weapons.
Secondly, he has the Khaine Awakened special rule, which was one of the big reasons for taking him in the last Codex, as he makes all Eldar units within 12" Fearless. Nice.
Finally, he gets his Wailing Doom, which is essentially a Meltagun. Not bad when you can run and fire it at BS10, if you think you're unlikely to get the charge why not. In addition remember that as well as being a Monstrous Creature the Avatar is a Character so he can precision shot.
One of the larger changes to the Avatar is the ability
to give him Exarch powers, however each of these will push him over the 200pts threshold.
First off you can take Night Vision, which sucks because he can't join units giving it to them and he has no use for it himself as his only shooting weapon has 12" range. Next, he can take Crushing Blow. This gives the Avatar +1 Strength, which isn't too bad, but you're not Instant Death-ing anyone new and if you want the extra stength you can always Smash. Next, Fast Shot, an additional shot with a Meltagun at BS10 is not bad, a little situational however. He can also get Monster Hunter, which I should really look up in the rulebook. Penultimately he can get Marksman's eye, which pushes him up to old Eldrad points but allows him to Precision shot on a 5+, although with only 1 shot it's still a little unlikely for the points you're paying.
Finally, you have Disarming Strike, which is quite spendy but gives you about a 66% chance of knocking a Power Fist off a squad.
To be honest, how do I feel about this new Avatar in comparison to the old one? I feel it's taken a bit of a hit. Yes he becomes a little bit more of a beatstick due to his extra attack but due to the nature of the weapons that are going to be fired at him like Missiles he's lost a bit of durability due to the Invulnerable save nerf. Plus, he's gone up by 40pts stock. I'm not sure if he's seen more, if competitive Footdar builds come out of this book then maybe he'll come back but as it stands I'm not sure. At almost 200pts you'll want to restrict how much more you spend on him, so honestly I'd leave the Exarch Powers alone on this guy.