I've had (in no particular order):
1. The transmitter battery go bad after one dive (with brand new battery).
2. The transmitter decide to eat batteries at a rate of one battery per month.
3. The transmitter to loose pairing (not transmitter fault, but effect is the same).
4. The transmitter to get the tiny tube plugged and not work.
I need a wrist unit (vision issues, I use split lens, and the close one has to be in your trailing eye, which is my right one, so the left is for distance). I use the transmitter to monitor pressure, show air usage after the dive, but I don't 100% trust them. I have a backup computer system also, so having a standard spg is a good thing.