I have the bamboo one. I've been wearing it pretty consistently since 2 days pp, my lo will be 4w on tuesday. I feel like it's really helped. This is my 4th, so my belly can use all the help it can get.
I also drank a lot of RRL tea during pg and for 2 weeks pp (1/2 gal./day)
I don't really have any ab definition, and I'm not where I was pre-pg., but I think it's certainly better than nothing. If anything I'm waiting for my extra skin to go away.
I do wear it when I'm out, I just turn the velcro to the back.
What I have to say about the belly bandit is that it is a giant PAIN to dry once you wash it (and I live in a very dry climate) it takes forever.