If you've got some Sims 3 chops, which most of us do, I can't imagine the career micromanaging of Ambitions resulting in a game-breaker. As long as you can kick your Sims out the door with all bars fully green, then what could possibly be a concern? Now, if you're constantly bombarded with messages requiring you to do this and that with your career Sim, then yeah, that could get tedious. We'll just have to wait and see.
My comments were directed more towards the issue that pops up when you constantly play with free will on as I do. Moving a sim through a dungeon while on vacation pretty much means that you'll be focusing on one sim at a time as dungeoneering requires high order directed actions to perform successfully. Moving two sims through separate quests while one or both are in a dungeon creates a hideous amount of "screen sliding" that is not fun to endure. Mainly this is because my monitor is good enough to give me mild motion sickness when the screen shifts from one sim to another by sliding the map at high speed to the other side of the town.
If work in Ambitions requires the level of micromanaging that dungeoneering requires, that will probably pretty much do it for me and working away from the house. I can multitask 8 sims while they are on the same home lot reasonably effectively by queueing up as many medium to long term events as needed (gardening, working out, fishing, skilling up, etc.), but once you have to start screen sliding to take care of sims on the other side of the map that's where things get to be a hassle.
Sometimes I just let free will run a sim that I don't have time for. Unfortunately, the autonomy in the game leaves much to be desired. A programmed routine that has the sim try to accomplish any of the locked in wants would be a joy to behold, but as it is now, it seems like my sims just run amok and cause problems for me to fix. I could turn the autonomy off, but then I'd probably forget someone and they would starve.