It seems like everything takes longer and there's less time to get things done. Relationships take longer to build and reach "friend" status, careers take longer to progress, there's more "homework" involved (daily tasks), Sims tend to get out of shape and pudgy if I don't play them, so I have to switch around to different houses and keep them working out, skills take longer to build, rewards take longer to unlock... it's more "grindy" overall. A lot of that is because of the multitasking thing. If you're doing two or three things at once, you're going to progress more slowly in all of them. But even if you focus on just one thing, it still seems to take longer.
I was watching the clock while a sim was taking a shower and it took almost an hour. A shower hour. That's kinda crazy. I heard there's a mod that changes the time scale so those little basic tasks don't take as long. I might look into that.