I honestly don't think its that cut and dry (as in good or not). It depends on the parent, and the child. It depends on your personality what you can cope with what you can't. If you introduce any type of comfort (even yourself) you have to be sure you can deal with helping them to give it up eventually. Don't start a trend if you don't want it to continue, or if you can't deal with changing it eventually.

I never had a problem with Paris, we introduced it to help her sleep and thats all she had it for ever. When she was 18 mths we took it when she got a cold as she wasn't using it, and she never asked for it again. Seth has one and he only has it of a night time or naptime too and he's fine

This type of discussion could go on for decades LOL you just have to know within yourself what you are comfortable with. And what's best for your child.

*hugs*
Cailin