I'm pretty new, but I enjoy going through all the items in the cache. It's kind of like my 'reward' for finding it, to spend some time sifting through it.
I don't think I've ever taken anything yet, but I always leave something that either matches the cache theme or that I think other people will like. I have a box in my car filled with cache goodies, and when it runs out I'll go to the dollar store.
My favorite item to find? New batteries!
Cat