So far the only thing I'm uncertain about is the Psychic phase. Aside from the piss-poor scalability of it and some broken as hell powers I quite liked the 40k7th ed Psychic phase. A few adjustments to how witchfire spells worked, how Warp Charges are generated and used, and a simpler dispel mechanic would have been great. That said, I liked Psykers even when it was just a flat leadership test so who knows - I'll probably still use a lot of Sorcerers.
One thing I've noticed is a lot of things people were moaning about have actually been addressed.
"Waah waah monstrous creatures are too strong and vehicles are bad". Ok, well now all vehicles have the same stats as MCs.
"Keep strength and toughness! I hate static rolls", fine they stay (something I'm happy about actually).
"Make leadership matter again" so now Space Marines are Ld7 and from what I hear most things are actually susceptible to leadership. Details haven't been leaked yet, so I'm still wary of exactly what that means
"The Psychic phase takes too long and is OP". Well now it's going to take about 30 seconds. How "OP" it is remains to be seen and depends on what powers we get. Again, a bit unsure about this myself but we'll see.
"Lascannons and other low-shot/high-strength weapons don't do anything". Variable damage stat, freaking amazing! Yes, a massive laser beam that is designed to punch holes through battletanks should do more than 1 point of damage per shot. This opens up a lot of possibility for dedicated anti-armour weapons and could see the end of "master of all trades" weapons like Grav cannons and scatter lasers.
"Heavy weapons on infantry suck" well they don't suck so much now that you can move and shoot with them! I can't wait to actually field heavy bolters - I've always loved the model but they have major issues getting in range of anything useful in the current edition.
I really feel like this edition is the first time in as long as I can remember where customer feedback has been taken into consideration.
To the people complaining about static to-hit rolls, we pretty much already have that. How often has BS6 or more actually affected your games? In combat you're usually hitting on a 3+ or 4+ in most cases anyway so I don't see the big deal of making it a set roll. Hell, if anything it adds some variability that's pretty uncommon in assault. Especially skilled heroes and combat specialists could hit on 2+, big bulky weapons that pack a punch could hit on 5+. Barely functioning masses of pulsating flesh could hit on 6+. Maybe the "Unweildy" rule becomes -1 to hit instead of a "Strike last" mechanic. I like this change.
Assault overall? Remains to be seen really. Charging hasn't changed a lot aside from having to be within 1" of the enemy instead of base to base. Initiative stat is gone so I expect something similar to the AoS alternating fighting with this "chargers strike first" bonus tossed in. I HOPE assault is good. I've always had an aggressive mid-to-close range play style and love getting my chainswords dirty.
Overall the thing that appeals to me the most is simplification. The last game of 40k I played was 800pts and it took nearly 2 hours. I wouldn't say I'm a veteran of 7th edition but I'm not new to the game and neither is my opponent. We were testing out units we weren't overly familiar with and he was toying with one of the new detachments from Fall of Cadia but what we expected to be a quick game lasted much much longer than it should have because of the complexity of the units we were using. Compared to earlier editions (4th and 5th come to mind) it was just LONG. I have a wife and young daughter, and spend roughly 4 hours total on the train each day commuting for work. Time is valuable to me, and I don't get a lot of it to invest in gaming. 2 hours for an 800pt game between fairly experienced players is just plain silly, and to me it isn't worth it.
So bring on 8th edition. Bring on 3 ways to play. Bring on "Grand Alliance" style factions, I'm sick of having so many books!
/endrant