Don't feel any guilt using a indicator, but I always use a dry fly to dropper, not a foam strike indicator, apart from increasing your chances using a dry fly, makes me feel better knowing that I'm not just using a float so to speak.
Depends on the situation, I mainly Czech nymph, but times when you can't, like slow running water over weeds say, the dry fly indicator comes into it's own.
You can fish water that you would by pass when fishing using the Czech method. Handy tool at times.
BlueFrog.