Allow membership payment by pledge
It's common to have a membership program that allows the member to pay by pledge. Rather than using donations and then crunching data via spreadsheet to determine "giving clubs", paying a membership by pledge allows you to leverage features like beginning and end dates, renewal reminders, and benefits, in addition to being able to pay by installment.
Separate memberships from transactions for better reporting
In the current membership architecture, there isn't a clean way to follow a membership's history and the membership dashboard is inaccurate. By implementing membership transactions, you can easily track renewal/upgrade/downgrade and determine membership performance over time. We currently report on donations to try to work around this.
Both of these are features of Raiser's Edge that organizations use quite often.