1. Can this plugin be tied into MailChimp? Is it compatible with MailChimp today (latest version, etc.)?
Yes, s2Member supports MailChimp and many of our customers are actively using that integration. There are no known problems.
2. Are you able to select groups of members to email regarding payment?
No, s2Member does not have any mechanism for sending mass-emails to members. Since the s2Member members are simply WordPress users, you could use a 3rd party plugin that allows you to send mass-emails. We are working towards improving this functionality in the next major release of s2Member.
3. Does s2Member calculate the details of payment – date paid, year paid, amount paid, etc.?
Yes, however those details are not viewable from within the administration panels. s2Member keeps track of them mainly for internal purposes. If you need to view a list of last payments or amounts paid, for example, you’d need to write a custom script that extracts that information from the database and/or write a custom plugin that records that information to separate database table whenever a transaction happens (this is made easy through the use of hooks).
We are working towards improving this functionality in the next major release of s2Member, along with making access to financial information from within s2Member easier.
4. And for example, with 300 doctor memberships, is there a way to sort by payment date?
No, there is no way to sort by payment date. That’s something you’d need to do from the payment gateway (e.g., PayPal). As explained in the previous answer, s2Member does not “manage” the financials for the membership; it deals with restricting/controlling access and handling payments through the payment gateways.
Again, we are working towards improving this functionality in the next major release of s2Member.