Never tried one, but judging from the slows on my old ice/rad controller, adn the big nerf-bat that was taken to the whole general strategy of stacking debuffs, I would guess that they are a lot less uber than you might hope for.
Ice primary is not bad but you should forget about slows..won't happen. Why? because all melee have like 50-70% res to slow (feel free to correct me), many squishies got slow resist IO and besides DR cuts slows to ridicilous low numbers that is not even worth it to count on them (unless you got heat loss that is like only power that still makes slow noticable lol).
How are Ice/ Dom's secondary effects (slows) in PvP?
I hate all this terrorist business. I used to love the days when you could look at an unattended bag on a train or bus and think to yourself.... I'm going to take that.