They're okay because they eliminate the bad installation factor. You're right that they offer almost no SIP though so I personally wouldn't use them every day.
Also if they've ever been occupied in an accident they're kaput and there's no way to replace them. So if I bought a used vehicle with one I wouldn't use it at all.
Pretty much everyone thinks I'm nuts. I don't let Gabe go anywhere without ME installing his carseat and making sure it's in right. Heck there are people already asking me when I'm turning him. Uhh he's only 9 months old so it's not even LEGAL yet, and two I'm not turning him at 1 anyhow.

I talked my pedi into giving people more information about the benefits of Extended Rearfacing and I carry copies of "are you using it right" to put on windshields of the REALLY bad offenders.
I just wish it weren't so expensive in Wisconsin to become a tech.