We use a few Opto-22 Output Bricks here and there. They have been quite reliable.
The problem with them is the space reqirement. Not like the ice cube relays where you can mount them on a piece of DIN rail and that is all the space they need.
While it may be true that the OPTO 22 brand of I/O does not have DIN mount devices, there are a number of manufacturers that do, Crouzet/Gordos is one example.
In addition, if space saving is important there is a vast range of DIN mount terminal type opto isolators available.
MURR, Phoenix, Weimuller etc. etc.
