What speed?

Speed 1 for daily life and most everything.
Speed 2 For walking long distances or up and down lots of steps.
Speed 3 When everyone is asleep.

Mostly 1.. sometimes I wish I could slow it down more. Especially while they are jogging. I let it fast forward during sleep, sometimes stopping it to work in their inventory ect.

Speed 2 cause I'm impatient.

Speed 1, 3 when my sims do something I want to be finished fast (leveling skills, sleeping, being at work, etc.) Never use 2 though, it's too fast for normal play, but too slow for things like the above mentioned.

Speed 3 for grindy tasks, 1 the rest of the time. I do even try to stay on Speed 1 if there is more than one Sim in camera view. Even if my Sim is grinding out a Skill or something, other Sims, even NPCs, can be very entertaining. You'd be surprised what's going on in the background. ;)

Lol at the answer above about staying on Speed 1 when they're sleeping. When I play a short time during the work week, it's usually a Sim day. I end up with them in bed, of course, so I usually watch them sleep a bit, then take the camera out into the dark neighborhood to listen to the nighttime ambiance. Then I go back inside to hear the snores, save, exit. I myself go to bed then, and it really sets the mood. :p

Normally speaking I play at 1. But if the night is taking way too long, and it doesn't automatically kick into speed 3 because the Butler is up doing stuff, then I kick it to 3. I find if I run the game too fast, I often miss golden opportunities.

Almost always 2.

Speed 3 more often than not since my sims tend to spend most of their time painting and the like. However, when they're just chilling with each other I like watching them.

Speed 1, unless I'm waiting for them to walk across a neighborhood or collect and harvest things. I don't get the point of being in a constant hurry in live mode. Seems to miss the point of the whole thing, imo.

1 because 2 and 3 don't seem to work well (as it should)