I don't have experience of using it myself but I do have (a bit of) professional experience with it.
It has passed third party (consumer) safety testing with flying colours - it's really good in that respect, nothing to worry about. It's actually one of the safest seats on the market you can buy right now.
The insert locks into the shell and the shell is angled so that any impact would go into the shell first, the insert is really just "cushioning" if that makes sense, for the baby.
I would say that once the baby has passed about 3 months old and their legs protrude over the edge of the insert thing it's less convenient as you can't really carry it as easily as their legs get in the way - a traditional infant carrier seat is carried sideways so you don't get this issue, even though they are heavier. You can also carry the Coral this way BTW - but in this mode it's actually one of the heavier seats on the market.
Also like any other lightweight infant seat the difference is really in the first 6 months or so - once babies get to about 6kg (which happens at about 4 months old) the 1-2kg difference in car seat weights really mean nothing compared to the massive weight of the child you are lugging around!
If you are looking for a lightweight seat which does well in safety testing but without the coming apart feature I would also look at:
Joie i-Snug
Nuna Pipa Lite LX
Avionaut Pixel (in UK this is branded Venicci Ultralite)
But overall, I really like the Coral - the concept is good, the execution is very well done, the newborn positioning is great and the safety is great too.