I use them off and on depending on the situation.
I use them on our local spring creek because the flies are small the tippets are light and the trout are finicky. They tend to spit out anything that doesn't feel right and the strike indicator helps detect the strike the few seconds quicker that make the difference. The indicator can also be used as a float to present the flies at any depth the fish are feeding at. I have had the day saved a few times by drifting a weighted emerger pattern mid depth.
I use them for trib fishing browns and steelhead because it helps to control the depth and bounces the flies along the bottom just right.
In larger free stone creeks I don't normally use them because I switch from nymph to dries and it is a pain to keep taking the indicator off.