• Can only look at users in groups of 20 – cannot customize to more
• Affiliate package costs extra
• Affiliate reports are done monthly and cannot be customized to be done quarterly
• Does not keep a log of affiliate commissions once they are marked as paid
• If you have multiple affiliate banners, you cannot customize affiliate emails that are sent out to be product specific
• Affiliate commission is global on all products and cannot be changed for specific products.
• If a user uses a coupon the first time he/she signs up for a recurring billing product, all future billings will be at the discounted (coupon) rate
• If you do not have a good user interface on your web server, the cron job can be quite difficult to set up (for the recurring billing)
• The payment amounts that show up in aMember do not always display accurately – amember customer support recommends using PayPal’s internal tools to track actual amounts.
• The recurring billing will work only with PayPal Standard not PayPal Website Payments Pro
• Broadcast emails are not saved, so you can't start with a template

Although it may look from the list above that the negatives outweigh the positives, that's not necessarily true. The cons that I've listed are fairly small limitations compared to the positive features of aMember. I'm happy with aMember and I'd recommend it.