To put it in properly you need a megger to check the installed cable before you bury it. Friends tried to skip that step and got unlucky and it quickly stopped working. Very few people have a megger kicking around so make sure you can beg/borrow/steal one for install weekend. I will get one eventually, but haven't come across one at a price that makes sense for me given its occasional usage.
The problem rate for electric floor warming is quite low. One manufacturer has a problem once every 3000 cables. However that is like a low rate of motorcycle crashes. It doesn't matter unless it happens to you.
One big problem is other trades damaging the cables.
People walk on them. Tile setters drop boxes on them and drop buckets of thin set on them.
I have a picture somewhere of the cable just laid and unprotected and someone had piled a washer and drier on it.
Another job, I assume when no one was around to keep an eye on things, someone went into the room where a cable had just been skin coated and obviously put something on the floor and used a razor knife to cut a shape. The cuts weren't noticed until the tile was down.
One manufacturer sells prepunched strap to hold the cable but the strap is poorly made and has burrs that can cut the cable, especially if someone trips over the cable and it gets yanked against the burr.
Some cables get stapled down with a crowned staples and while day dreaming a staple goes through the cable instead of around it. You can get a special stapler that is more protective but it costs a bit more.
Tilers can get aggressive in cleaning out grout lines.
If the damage is minor repairs aren't a big deal but not cheap. More than a new cable but it saves the tear out costs.
The controllers aren't cheap but have GFI protection. Sometimes to save on controllers installers use a contractor to power a number of cables. Great! The GFI function now only protects the coil of the contactor. If there is a fault in the cable, over current can cause massive burnout.
One of my favourites was a job I checked out when the installer wasn't able to attend. I called him later to discuss some discrepancies. He explained that it was his first installation and he was so concerned he read the instructions over five times. He said he still had the instructions as they were in the box with the other half of the cable.
I asked him to get the instructions and read item 5 in the warnings. He started reading Do not......cut............the.............cable.....silence...
I wouldn't sweat blood over an installation but beware of the clumsy worker.