What I like about AoS:
1. The game is easy to get into (great for the hobby in general and for gaining new players)
2. The getting started kits. Cheap (for GW standards) and friendly for beginners
3. games are fast
4. making lists with points for matched plays is incredibly fast. 5 minutes and i can do 2 or 3 competitive lists.
5. units move fast, even the slowest ones are much more manoveurable than the ones in oldhammer
6. it's not just a skirmish game, at 2000-2500 pts you field a whole big army. It's just that the kind of approach to battle is more similar to modern armies, rather than napoleonic ones.
7. Monster's getting less effective as they are wounded - neat idea.
8. Mixed armies, cause finally i can field that allegiance of Dwarfs and Empire.
9. Synergies rule the games, and thanks to that, everything can be more or less effective
What I dislike about AoS:
1. destruction of the old world.
2. discontinued armies. I hate that.
3. Sigmarines and Seraphon can't die, and if "slain" in battle they just reform. What is at stake?
4. the rules are spread out all over the place rather than neatly organized in the BRB + army book. You need the battletome of your army, the general's hanbook, the allegiance books...
5. some of the new names (Khorne grinder of bloodied skullgore and similar)
6. no more ranks/flanks, with associated bonuses/penalties. Napoleonic war is fun.
7. despite the customization with artefacts and Allegiance abilities, heroes and wizards feel much more generic.
8. Mixed armies. I like to play the strenghts and weaknesses of my beloved army, not to play an empowered mix.
9. movement is sometime excessive. Certain armies can enter in melee with you in the first turn and devastate your line before you begin to play!