So, it seems some people do actually have their hands on the 7th edition book now (reputable folks at that) and the changes are getting laid bare. I thought I'd lay out my pros and cons from what we've seen so far.
I really was hoping for a bit more if I'm honest. I like more of the changes than I dislike, but barring the addition of the psychic phase, this feels like it could easily have been an errata rather than a £50 set of books.
I really don't like the idea of the daemonic power tree. it just sounds shit. Units that create brand new units are usually pretty awesome. When introduced, i think the tervigon was over powered, they perhaps nerfed it a bit too hard in the recent book, but letting any psyker except grey knights summon squads of blood letters or seekers or whatever?
it sounds game breaking, and oh look, the sales of daemon models has sky-rocketed!
Psychic phase. while i like the idea of the psychic phase in principle. I, as Dave has mentioned previously, often find ive forgotten to cast a power when i was supposed to as they're all supposed to be cast at different phases, consolidating that into 1 phase will help no end. but the 'power dice' bollocks from fantasy was unnecessary. they could've made it a phase, kept the casting method as is and allowed the opponent an opportunity to deny the witch for anything and that would've been fine. This kinda of feels like they felt they needed to change it as much as possible as they knew the 7th updates were a bit thin on the ground otherwise.
Perils of the warp table. Its a D6 roll on a 6 result table? Uh-oh. Half of them involve a leadership test? Uh-oh. Some of them are bad, some meh, and one quite good for you? Bleurgh. Swingy tables, less of them please!
They didnt make any of the rumoured changes to help assault. i did have genuine hopes for consolidation into combat coming back. My bad for believing the wishlisting, but it would make sense i think.
Charging through terrain is a flat -2". Excellent, while i still don't like that assault is 2D6 inches, knowing how much terrain is going to affect the distances you need every time is an improvement. How often have you had to attempt a charge through a ruin, needing, say, 4"and you roll a 6 a 2 and a 1 and fail to make it (getting shot in the process).
Move through cover lets you assault through terrain at your full 2D6". Makes sense and saves having to remember how it used to work (i honestly cant remember at this point how move through cover affects you assaulting through terrain in 6th).
A weapon with skyfire always snapshoots at ground targets. This is a bit of a cack handed way of fixing the weird interceptor dual-rule, i expected them to introduce a 3rd layer between skyfire and interceptor. Skyfire - Shoots at flyers normally, ground targets snap shot. Multi-tracker targeting system(?) - can shoot at ground targets and flyers as normal. Interceptor - can shoot at things that arrive from reserve.
Anyway, i guess it solves the problem.
Jink is a 4+ cover save but if you choose to jink you can only snapfire next turn. This is kind of a plus and a minus for me, overall i think the changes are good for the game, but i do think theres a fair few units i own that have taken an effectiveness hit from it. On the other hand, the fact that the cover save is improved is quite handy for a few units. The standard loadout Wave serpent now has a 3+ jink, but only hits on sixes the following turn, having the scatter laser mitigates the effect somewhat, but its still not the powerhouse gunboat it was. Which is probably for the best. I suppose that also increases the survivability even greater, am i going to bother firing the serpent shield every turn if its only hitting on sixes? albeit with a reroll? Maybe not.
On the other hand, something like the venom, ive now got the option of using a 5+ invulnerable save and shooting as normal, or a 4+ jink and snapfiring. Its an interesting one, and i think its generally a positive move. I'd be curious to hear how folks with bike armies are viewing this change? I'd also like to find out how jinking affects assaulting in the following turn, if at all.
Primaris powers, if you roll all of your psychic powers from the same table, you get to take the primaris in addition for free. Nice little change. Not much more to be said.