I have one, although I only use it for storage really... Ongoing projects go in my backpack and I work on them at work (while I'm on hold, waiting at court, etc)
For me, a zipper is essential, because if I leave my floss in anything my cats can open, they go nuts and eat it/drag it around the apartment/god only knows what. Learned this one the hard way. It also has a little pocket for scissors, but I usually forget to use it and just throw mine in on top of the floss.