This is a problem in both the old version and the new version.
Before arguing that new programs based on new technology will have higher memory requirements, I've not run into one with quite the drain as RSS Bandit..
Upon starting RSS Bandit memory usage is approx. 30MB, which is high in itself..
After using the default feeds installed with RSS Bandit, my memory usage is now sitting at 71MB.
After importing a number of feeds and updating them, it's at 92MB.
It would seem that there is no memory management going on, you should do whatever you can to release memory when it's not needed (destroy objects, arrays, variables, etc).