I have seen a lot of rambling on the Internet concerning the new Nidz. There have even been some batreps posted using the rumours. I am not sold on much of what I have read and am waiting to get my hands on the codex until I make any comments as to how I think they should be played. The Nidz look like they are going to get a major rework going by the rumours. Obviously they are going to have to be able to bust armor at range to be a potent threat to the current metagame. I think they will be able to tank bust at range. My main concern is that a lot of the best choices are vying for your three available slots in the FOC as Elites. I really like the deathleaper since his presence can effectively shutdown psykers. -3 to Ld for psychic tests is huge and you can't get around that plus he will nerf psychic hoods trying to shutdown your Zoies. While Hive Guard are nice and I like the new minis I think from what I have read Zoies plus the deathleaper are the way to go versus armor. There are those people who will inevitably always say if your list can't take down a landraider then it's no good. I think that is a fallacy as more often than not you don't see any landraiders BUT a S10 AP1 lance in the face is pretty darn good. Basically you have S10 versus AV12 with +1 to the AP table. If the shot goes off you have a 67% chance of scoring a pen with a 67% chance of either immobilizing or blasting the landraider... That's why you need 2x 2 Zoies. You can bring them in behind the Trygons so you should definitely be in range. An immobilized landraider is chump change versus monstrous creatures in close combat. More importantly the Zoies can take out guard armor very well.
There must be a reason why Nidz lost universal fleet across the army. I reckon this is due to their now being able to enter a huge portion of their force via deep strike and outflank... So I think you will be able to design a list that can deploy in a variety of ways optimizing how you face off against other builds. It could be a beautiful thing and deployment is going to be very important for the new Nidz.
Currently I am thinking that genestealers are still the best troop choice with outflank and fleet. I also think the Alpha Warrior podding in with a a Warrior crew will be an excellent choice... They are a shock troop and some armies won't have the dedicated firepower to take them out before they can charge. They will be awesome in assault.
I am still trying to figure out what is the best choice for the primary HQ. Obviously a Tyrant is going to be popular so it's a matter of deciding whether to take wings or walk him on with Tyrant Guard. Hive Guard sound like they will be very situational and as I have said I am sold on Zoies. If the Hive Guard could ignore cover saves then I think they would be a no brainer but going by the rumors that's not the case.
So in conclusion the good units based upon the rumors are as follows:
Alpha Warrior with Warriors - spore
Genestealers (maybe one squad with a Broodlord)
I'm not sure about the rest but the squads above could easily build your core. If you have a good core then your other choices don't have to necessarily be great choices as well, you are looking for synergy and keeping your synapse online. The new rules for basic instincts are better now for sure BUT you certainly won't want to have to rely upon them versus a good gamer... It's like handing the keys to your car over to your worst enemy. I happened to see a comical post on another blog in which the poster stated you only have to apply basic instincts if your models are facing in the direction of visible enemy units... Like I said I think it was meant to be a comical post but on the other hand that person lost all credibility with me for posting it as a tactical article.