ORIGINAL: Mykey
I think it's best to relax the stringif at all possible but the string separator does work and is especially handy in a crunch situation. They don't cost that much and it certainlydoesn't hurt to have one in the bow tackle box. I've used mine quite a few times and have never damaged a string with it, you just have to take your time and be careful.
I have and use one however I also agree that it is probably best to relax the string before doing this. In a pinch it will certainly get the job done though.