New version of aMember uses brand new API for payment and integration plugins. It means all plugins must be rewritten to be compatible with new version. I believe someday we will rewrite all 100+ currently implemented plugins, but there must be something to start with. Currently we have implemented the following plugins: PayPal PayPal Pro PayPal Express Authorize.Net 2Checkout SWREG Please let me know what other paysystems you personally need to start use v.4. Just post payment system names.