I have them and I use them for my friends kids and some of my foster kids depending on what kids are with me and if 3 across is necessary. Right now I have a Regent and an EFTA in my vehicle (casted baby and need the wide seat) so if I transport any other child I need the RSTV.
I feel like I'm answering a lot of questions about the RSTV these days! Anyways, I have them in both sizes in the old style and the new style and I love them! I wouldn't use them outboard unless it was a 100% emergency had no other choice, but I feel comfortable using them center especially with other seats next to the child. The new version only has 1 clip and is more open in the sides and back. It's not as stiff. The new version has sort of a flap for the lap belt whereas the old version has just the vest which is rather stiff. The only version fit older/ bigger kids well, but kids around the lower end of the limits it just didn't bent to position the lap belt correctly on some kids.
The bottom line.. I have it, I use it, I love it! I've been in a bad accident with mine and the child that was in it was perfectly fine. The children in the 5-pt harnesses complained of neck, shoulder, and hip pain along with getting little abrasions from hitting the sides of their seat. The child in the RSTV didn't budge even far enough over to hit their head on the car seat next to them. It was the only person in the car that didn't get banged up and had weeks of pain meds doping them up because of muscle strain.