2 passes seems to be the sweet spot (and reduces how frequently people roll for initiative). and it's pretty easy to get to this point in SR4 (edge,gear,drugs,magic) regardless of character archetype.

for goons, I usually have them take 1 IP unless they are aware that the opposition is significantly faster (not every guard in a normal facility is going to take a hit everytime something moves across a remote camera) and then edge up for a second in round 2, or retreat and attempt to regroup/drug up for later combat.

elite security forces (zero-zone and R&D and special ops etc) are a different story of course.

I have 9 players at my game table (not all play all the time)
3 have 3 IPs : a physad, a mage(level 3 sustained focus) and a sam
2 have 2 ips : a sam and a merc
the rest have 1 : soc ad, shaman, hermetic and decker.
I must say i limited them at character creation, but it works good like this.
In fact, the sam says he doesnt think having 3 ips is worth it : their tactics is to play on surprise, thus its often just a reaction roll to see if they can act before the opposition realise they are there.