I know this halon is very toxic but in a few years of flying nor I or my colleagues ever used it. We know we have it there and that its very effective. Id rather be intoxicated with halon and treat my lungs than hving a fire out of control in the cabin cos we all know its over if that happens.
Actually the toxicity is said to be very low:
http://erd.dli.mt.gov/safetyhealth/brochures/halon.pdf