Spirits and drones only get 2 IP, actually.
Finally got home to check my books. SR4A p. 167:
"Drones that pilot themselves have an initiative equal to their Pilot + Response attributes and they get 3 Initiative Passes per turn."
So I guess we were both wrong on that one. I concede the point on Spirits, but I'm almost certain that some of them used to get 3 or 4 passes per turn. In any case, Spirits of Man have Innate Spell as an Optional Power, so if our fictional "Killer GM" really wanted to do his thing, he has more than enough tools....I don't think the IP system really advantages players or GMs over one another; I just think it creates a bothersome sameness and makes combat kind of weird.
I mean, if I have 1 pass, and you have 3, and I'm after you in initiative, that means I'm fast enough that you can only take one action before I do, but then after I take my action I'm so slow that you can take two more actions before I can do anything. It's kinda weird if you think about it.
But, I said I was dropping it, and I will.