I also use Freeze +P at work and it's very effective. You'll always get an individual that is somewhat resistant to it (a lot of guys who've snorted a ton of drugs in their lifetime are very resistant to its effects on the mucus membranes), but that's the case with most chemical irritants. If you haven't done so, make sure you get some exposure yourself so you know what it's like. When using chemical irritant, you're bound to get some secondary effects. Of course nothing beats macing someone and having your coworker on the other side of the guy, missing the intended target and hitting you.

Fox Labs stuff has a good reputation as well. I've never used it, but some of my coworkers moonlight as rent-a-cops at area hospitals and that's what they use. They say it burns a lot worse than the Freeze +P (although it lacks some of the other effects since it's just OC and doesn't contain any CS).