I saw this and I want to try it. I have 2 problems though - one, since I carry my lunch bag in my purse, I can't guarantee that it won't tip over and mix while I'm commuting, and then the lettuce would get all soggy. And two, I don't bring my lunch in glass containers. I'd like to but it's too heavy (gotta be nice to the back) and I'm worried about breaking them if I clonk my bag down on something. I guess I could do it in a plastic container though, it just wouldn't be as cute.
Right now, I take the wet ingredients (dressing, tomatoes, maybe a couple of other things) in a separate small screw top container from the main big container with lettuce, etc.