I've read through the "leaked" PDF and FAQ, and I am of a mind that it's legit, a draft that will be edited and cleaned up but largely unchanged. I won't go through my reasons why I think so, but I will state why I think Nids will finally pull their faces out of the digestion pool and get to chompin' everyone. Here's what I've found:
Positives:
+Only what covers the base counts as the body. Those of us with huge Harpy conversions (like mine) or other beasties have major problems with LoS. Now it's a lot clearer, and we'll have less arguments. Furthermore, dense terrain will help hide us.
+With the changes to WS, Deathleaper and the Swarmlord will be hitting on 2s, and many troops will need 6s to hit back.
+No more missiles causing ID on Warriors. They'll take two wounds instead, though S10 will still insta-gib them.
+Reserves are more controlled. You can get the Doom down earlier more reliably. Lictor's Pheremone Trail is actually useful as it functions even when they're off the table.
+Genestealers have Move Through Cover, which means they'll reliably get where they're going at a quick rate.
+Along those lines, with running being doubled movement, it is quite possible to get our assault troops into CC by the second turn.
+With much of our troops having Fleet, that means charging 16".
+In CC, No Retreat wounds are divided, not suffered by each unit. So when you've got a swarm of Termagants and a Tyrant in combat, the Tyrant won't have to save a bajillion No Retreat wounds. Plus it can be negated.
+Objectives. You get points every turn for holding an objective. It's really easy to throw a horde of spawned Termagants on an objective and camp them there all game. Furthermore, you can't hold an objective while in a transport. That means the hardest part of playing against Mech, getting them out of their shiny metal boxes, is already done for us.
+Infiltrate and Deep Strike. From what I read, you can assault after deep striking. Lictors can deep strike anywhere without scatter. However, you must beware of defensive fire.
+Nids need terrain, and there are stratagems that let you practically rewrite the battlefield.
+The Tyrant can now leave Tyrant Guard. I'm not sure when you'd need to, but options are always good.
+Hormagaunts can choose to use Fleet and run up to 16", or use Bounding leap and charge up to 18". They are faster than Beasts and cavalry while running, though their charge is slower.
+Harpies now are far more useful, and you'll actually get to use those spore bombs now.
+Pyrovores get a 3" boost in their range, and can use their flamer in close combat. It ignores armor saves in CC as well!
+Trygons can assault after deep striking now, just watch out for defensive fire.
+The Doom now inflicts two wounds per point that they failed the leadership test by, but no longer fires in the opponent's shooting phase. This is better because most of the time, the opponent just moved out of the 6" bubble.
+If you're in a transport, you can only shoot out 18". No more getting splatted by Mech Guard autocannon spam!
Negatives:
-S10 will cause two wounds to anything with T6.
-They can run us over with their tanks. Tank shock isn't a joke anymore.
-You can't stretch a big conga line of Termagants out to claim multiple objectives. One unit per objective.
-No more blocking off table edges. Reserves are simply placed within 6" of the edge.
-The Mawloc can't deep strike into CC anymore.
Interesting tidbits:
*You will likely need to model special Termagants and such to serve as squad leaders. I think a simple spike on the head should suffice.
*Blasts work like they did back in 2nd edition. I am not sure if that makes you more or less accurate. My guess is more.
*There is mention of a transport called a Cerebore. Are nids finally getting a proper transport?
*There is also mention of a terrain piece called a Weathered Bastion. It's not a regular bastion, it's old and tattered with reduced armor value. Possibly a new terrain kit? I'd put money on it.
As you can see, the positives outweigh the negatives. I may be doing a test game on Tuesday, I will report on how Nids fare with these rules.