Note: copied from posting on WishList help forum.
Issues of integration with MailChimp and Extra Data Fields
First, I want to thank Mike for the enormous amount of help he provided to me on this issue. With his help, we have figured out what was my problem with my integration.
However, after having done that, there are a few issues that should be posted, and hopefully fixed soon.
1. When integrating with MailChimp (MC), you CAN'T make any changes to the sign up form. If you do, there will be NO connection between WishList (WL) and MC. (This has been tested and confirmed by me...with only a single addition to the signup form in MC, all connections were lost).
2. If you want to have confirmation of the signup (double opt in), in WL, you MUST use the WL e-mail form to do it. You will NOT confirm your subscription in WL by just confirming on the MC opt-in form. This is a problem, which requires 2 opt-in's. (Bummer).
3. If you have additional fields to an "update your profile" in MC, it looks like this also breaks communication. (just tested).