I've never thought app.net was a good idea for many reasons but I think this is a good move. Introducing a monthly plan is the smartest thing they could have done. With so many yearly plans starting at the same time (when it launched) they could have seen a big drop in users as people reevaluated their decision to purchase in a years time.

With the $5 monthly fee I think people are more likely to continue paying for it - there is no time where they will be forced to reevaluate the value the service provides.