I've just finished this integration using the wpmu dev membership plugin..
I've set it up so that membership processes recurring payments and assigns an subscribe the 'unlimited posts & unlimited time' corresponding wpuf usermeta, and on cancel reverting this meta back to non-payment status. This was possible with the wp mu dev plugin, as it supports pings on join and cancel which in turn can trigger scripts to modify these usermeta values.
This allows users to purchase a single pay to post, or to signup and get unlimited postings on a monthly fee..
Also for the clients ease of use, I've coded a panel to control both plugins pricing, payment gateways, and to show a compiled transaction log from each with filterable views of 'subscription/token' transaction types, and 'start/end' date to transaction times.