For recreational cutting, I prefer non-serrated blades, but all of my "automotive rescue" knives have serrations (and Spyderholes). Based on the experience of others, the time saved counts. I've not had to use them yet, but I've not ever had to use seatbelts or airbags yet either. If the time ever comes, I'll be happy to have them all.

I might add that at the last several accident scenes that I've stopped to help out at, there seems to be an increasing number of airbag related injuries. One elderly gentleman was quite dazed after his deployed, and it had evidently smashed his left hand into his window. His wrist was swelling up rapidly, and he was in a lot of pain. I witnessed the accident, and was in his car in 20 or 30 seconds, so this didn't take very long. I seriously doubt that he could have had the dexterity to open a stockman or SAK. It made me re-think my whole strategy. I vacillate between a Spyderco Rescue (fully serrated) and a pair of crash shears.