I'm really racking my brain here.... I did learn some positive lessons as a jw, but all of them were as an adult, so they don't really fit into the 'growing up' category.

The big one I can think of, is not being allowed to do normal childhood things (sports/social stuff), is that it forces you to be very creative with your time. There would usually only be one or two kids my age in the hall, so it's not like we could organize a soccer team. So we'd make up all sorts of different games whenever we played together. (think Calvinball) I kept doing that even as an 'adult', and it gradually turned into a career in game design. (not to mention a fun hobby)

There's also the emotional fortitude to stick to your ideals even when it's difficult, or not socially acceptable. Ironically, always following my 'bible trained conscience' despite what your peers say is what made me leave the jws. If I hadn't had to endure ridicule for my beliefs as a kid, I may not have had the strength to leave once I found out they weren't true.