I had my first game of Rockethammer last week (It's rockethammer because there are no jump packs in fantasy, but oddly one on the rulebook for fantasy) and I learned some things about the state of the game and my armies.
I played my Vampire Counts against a largely Khorne Warriors of Chaos army and it didn't go well. I was utterly decimated and killed 6 models. Actually it was less then that because he cast Purple Sun and it didn't go well once and he also had a miscast at one point so he may very well have killed everything.
I like to take any crushing defeat as a learning experience, so I will forego the "Vamps suck" rant that has become so common. I think Vamps were weakened, but that's alrgely because they were jacked up in 7th. The fact that Initiative is more important and chargers strike first did hurt because the VC Inits go from bad to worse. Vamps really don't have anything super-hitting like they used to. Even the Vamps themselves aren't too capable against the wrong challenger. Nothing they have is all that decent in a fight and they have basically no durability. Depending on who you play they can do some damage, but against a strongly offensive army, be prepared to lose a lot of combats.
Now the strengths...they can replace losses so the fact that they can't take a pounding is somewhat negated. The only time this becomes a problem is if you start losing more models then you can replace in a turn. As I said, you will lose combats, but the good thing is you will never break. You're going to lose extra models, but you won't be overrun so you can tarpit units.
As for 8th in general, I have to say Magic has been severly nerfed. Yes, spells are powerful now, but the "Winds of Magic" roll means you can't build an army that has to rely on magic as its biggest strength. When you really need to get a few spells off, be ready to roll snake eyes and have no power dice. I also think this means the game doesn't scale up well. At 2,000 points an average roll of 7 dice with maybe a few extras channeled would be plenty, but at 4,000 it's nothing compared to what you could have in 7th. I like the changes to combat, espically the casualties coming off the back. Combats are more decisive and the game moves along better.
As I look forward to the Empire army I'm working and the Warriors army I've decided will be next, I'm beginning to see that like 40k's 5th edition before it, armies have to change to keep up. Unlike 5th, armies seem to be far more balanced, but only time will tell if the approaching army books follow the pattern their sci-fi counterparts had with the over-the-top IG, Wolves and Blood Angels, but we will have to wait and see.