We didn't have any problems with social classes with the previous editions, the GM chooses the difficulty of rolls depending on the situation.
I always read the same thing about losing less rounds in combat but you can have a player with 60% fighting an enemy with 60% and fail 50% of times, if you keep losing advantage things can get worse, so much for not wasting rounds... Advantage also makes things more difficult to the DM.
If you are a magic user and you want to cast a spell of CN>0 you could spend rounds channeling until you get the needed success levels to cast the spell and then fail in the following round. You have more chances to lose rounds in this edition.
The way to solve a career dead end is to repeat a career. Staying in a career up to level 4 sometimes it makes sense, other times no, for example I don't see how it makes sense that someone of high level and reputation would love to continue being a rat catcher. The new system also gives level restictions, you want to be a troll slayer with a 2 handed weapon, wait until giant slayer, then you can also improve your toughness. It's different but I'm not sure this is an improvement.
Experience is the same, you spend it on skills, characteristics or talents, but now you depend on the tier of your profession, the level of your characteristic, the level of your skill and you improve the last two by 1%. More difficult, slower and prone to errors to gain nothing.
The art I don't think it resembles very well a medieval world and what is warhammer and in this case Reikland, they only left trolls, orcs, etc of different genres and professions to make it more like world of warcraft.
Compared to 3rd edition you don't need to buy special dice, more books to play with more players, etc. The system in my opinion went back to be an rpg and not a mix of boardgame and rpg. The adventures we'll see, the third edition had some really good ones, we did two campaigns, the enemy within and another one using most of the other adventures in one area of the empire.