A few things-
All seats that pass FMVSS are safe to use if used properly. So this is a safe seat. So is the $40 Cosco Scenera, $80 Evenflo Sure Ride, $200 Graco Headwise, $300 Britax Advocate and $500 Clek Foonf. When you buy more expensive seat you are buying bells and whistles- nice fabric, nice comfort padding, ease of use, a brand name, etc. I use to say you're buying a seat that'll last longer, but the Evenflo Sure Ride will outlast the Britax Advocate by years, so that's not true anymore
Both the NHTSA and the AAP recommend rear facing until at least 2- the Kiddie will not rear face. I would encourage people to try for closer to three, continuing as long as the child fits and is comfortable. Everyone would be safer rear facing, it's just a bigger deal with little kids because they are more fragile.
This seats works differently than five point harness seats. Theoretically it spreads out crash forces better than a forward facing 5 point harness, but not as well as a rear facing seat.
The big concern I have is Kiddie has repeatedly said that a child who lays their head on the shield (as 2-5 year olds will do) is out of position and not safe. I am not happy about this, at all. It effectively makes it the same as a belt positioning booster-the major point of using a forward facing harness seat is kids are wiggly and do not hold still. If this seat requires a 2-5 year old to hold still it isn't acceptable to me.
The other big issue is the weight limit. Britax use to have a seat called the laptop, that used this technology and could be used to higher weights. If you buy this seat, and your kid hits 40 lbs at 3 or 4 years old, you will be out spending $80+ to buy another harness seat, because children simply aren't safe in belt positioning boosters at those ages (sometimes you'll have a 4 year old who can sit in a booster, but that is rare).
I know people who just use the booster for kids 5+, and it's a good seat, I have no issues with it! So if you want to buy it for a bigger, older kid ready for a booster go on and do so!