There are various different systems on the market. Merc took the best one and improved it (or so they say).
Having actually driven two new Mercs with the cameras, I’m pretty confident that they are better than mirrors, plus the blind spots are much reduced. They pivot in turns so you can always see the trailer, and cope well with light and dark with good contrast control.
You can set them up to the length of the trailer, there are lines on the mirror to indicate exactly where the back of the trailer ends.
A period of adjustment is needed to get used to them, and I suspect that the longer you’ve been driving the longer that period will be. There is a moment of panic when you look at where the mirror would be, and it’s not there.
The camera is in a sprung fairing, and less likely to get smashed than a normal mirror.
TBH, I was not so impressed with the rest of the truck…the Gigaspace doesn’t have the ‘wow’ factor that a DAF XF or big Scania has, and I’m not convinced of the merits of replacing the secondary switchgear with a giant iPhone nailed to the dashboard, but then I am old and stupid.