First off, those Tide-to-Go pens are great; they'll remove stains/marks fairly easily and quickly without having to wash the clothing. It's especially useful for a small stain on something clean or something you don't want to wash, like a sports jersey. However, they smell like shit.
Anyway, the only beef I have with these pens is their smell. It's awful. Like shit, seriously. You almost have to wash the clothing after you use the pen anyway, which kinda defeats the purpose.