HQ - I won't do the stormlord or trazyn as i don't have their special rules yet so i cannot make assumptions on nothing
Overlord
Pretty much the same as the old Lord, can't remember if lords had WS5 BS5 or not but these guys are one down there, have a 3+ save with the ability to have a 2+ save and a 3++ save and some other nifty equipment like the tachyon arrow which is a hunter killer but S10 AP1 with infinite range so be careful their. Treat them like a termie captain with a stormshield and a one shot railgun i say. Nothing to special but can still become T6 destroyer lords so that could be an issue
Necron lord
Now demoted to being in essence a commisar, a normal commisar, these guys take no roll in Force Org, they form a council and can split into lots of smaller units, but they can join together to form a royal court like honour guard, becoming some power house squad as they have similar wargear to that of an overlord but starting points are that of a commisar. 1 wound though means they are easier to kill but be wary again
Cryptek
These are in essence the psykers of the necron army, capable of changing the game around them and boosting stats of smaller units, they are like Necron Lords in the way they are organised but can take alot more options and can chose one of 5 harbingers to become, as a royal court consists of up to 5 models they could have every ability at their disposal.
Elites
C'tan shards
They are back and this time once again, our lasguns are useless. literally. Their statline is amazing for an elite unit, their S/T7 and 4 wounds, 4++ save A4, their tough and they can now have 3 of these. their abilities are similar to that of the nightbringer and deciever but they can now mix and match 2 per c'tan. I'm worried about these guys as they can have so many but i'd assume they will cost a bomb. Just don't field blobs against these guys and you should be fine.
Deathmarks
These guys are their new snipers who can come in the same turn as a unit from YOUR army that has just arrived from reserve as well, not to bad for reliable reserve rolls and they get to choose one unit they seem to hate, they then get to wound on a roll of 2+ afterwards, amazing against MC but meh against guard as it's usually a 3+ anyway. they're also range 24" snipers but their also rapid fire, slightly odd but awesome as well
Flayed ones
No different really, still amazingly large amount of assaults for one unit but their still weak, being I2 they we go first in assault!
Necron lychguard
Heavy assault units, very heavy, stats of a normal overlord but you can have a tonne, swapping out their warscythe (S7 in any assault!) for tesla pistols and dispution shields (4++ save) make them very durable to fire. Still only I2 xD
Necron Triarch Praetorians
What? Necron jump infantry? Noooo you must be wrong? no its set in stone (or paper nowadays), these guys are the shooty version of Lychguard, same stat line just with S5 AP2 assault weapons (very short range!) which are power weapons in assault, i say don't underestimate them if your a space marine, AP2 isn't any different to AP4 to us really.
Troops
Necron warriors
They've been nerfed. heavily. They have only got a 4+ save now, don't always wound on a roll of 6+ anymore and only get up on a 5+ now and if the entire unit is down, they can't get up at all. even with a necron lord (Who allows you to get up regardless of how far away you are (have to be in coherency now) BUT, they are only 12pts a model now and as they still glance on a roll of 6 (with gauss rule) they are more a problem to us than any other army
Necron Immortals
Finally a change in their troop organisation. Exact same stats as warriors but with a 3+ save and their old points cost (maybe 20pts cant remember) but with better guns. Much better guns, Gauss flayer is still pretty good and the tesla gets double hits on a to hit roll of 6 and with rapid fire this could be a problem. I imagine more necron players taking these in large numbers like we would take HWS if they weren't in platoons all the time.
Dedicated transports
Ghost ark
This is the first of the new vehicles, an open topped, AV11 transport? hello autocannons, but wait, it has a rule which means for every unsuccessful damage roll, it gains an AV of 1 for each side, by up to 2 AV points, this means it can be AV13 on every side. That is insane imo, you need to take it out, and fast, dedicated to only warriors as i can see. but they can shoot out either side, no foward shooting points even though its open-topped. it can also repair warriors D3 a turn, this looks like their medic vehicle and will tempt necrons into taking warriors of immortals, expect many of these in one army. It also has living metal, this has been nerfed quite a bit, it ignores a shaken result on a 2+, and a stunned on a 4+, thats it. Get your melta ready boys!
Command barge
This is basically a chariot transport with same rules and AV as a ghost ark, dedicated to the necron overlord and no one else, it allows him alone to shoot out of it and assault whilst in his vehicle, very fast, very versatile but looks like a gimic to me, i wouldn't expect many to be bought except for fluff reasons unless it is dead cheap or it has amazing special rules
Fast attack
Destroyers and heavy destroyers are the exact same as before. no difference i can see.
Heavy support
Annihilation barge
Its sounds dasty and is nasty, a weapon that shoots at a target once, and any model within 6" of its blast (S7 AP2 blast) suffers a lightning strike like a tesla pistol (S4 AP-) so it could be nasty for us guard and our ranks
Doomsday barge
a HUGE gun, its the ghost ark but no infantry transport, has same rules and stats as ghost barge and is THE largest gun in the standard game, a S9 AP1 Large blast weapon that has the range of a railgun, this will decimate tanks, decimate infantry, decimate anything that is under the template. The name is a very good description of the weapon. destroy it quite and efficiently, it will only get harder.
Monolith
Its still here, its still big and its probably even worse, the living metal rule is gone, but you can't get within 6" of its door without getting sucked into the necron phase world on something like a 3+ and INSTANTLY removed, its like a vortex missle but larger and constant, its meant to keep melta out, best weapon of any army by far to do any damage is the vanquisher if it hits, then melta if you survive, then Demo cannon, moved down a bit from best. Its only 200pts now, meaning more points elsewhere.
This is only based upon what is on the advanced orders, whatever is in the book could be more menacing and from the rumours of the special characters, they sound really mean and like space wolves, you can have more than 2 HQ's.