I have used them before and now I don't. Pros for their use: Makes the water clearer. Cons: I had to change them every 5-7 days, had to clean them, had to buy them when they ran out.
Right now, I have an external overflow, which has flexible pvc piping from the bottom of the external overflow box, like those used for pools. There are two outputs from the overflow box and one pipe that leads to the sump. The flexible tubes drop down to a PVC junction I designed. This junction is made of hard PVC pipes and that pipe drops the water for the skimmer into that compartment and then the rest goes to the fuge compartment. The flow to the fuge compartment is controlled by a ball gate valve after the junction to the skimmer. I don't have a way to get the water in the overflow box through a sock and then into the PVC pipes. I could throw a sock under the pipe that drops water into the skimmer compartment, but I don't have much room, so I am not using them now. No mess to clean up now. Some people say that the pods from the fuge won't make it to the DT with a filter sock, but it's not an issue with my design, because in my setup the water flows out of the fuge to the return pump compartment.