What ZuneInsider said that there are no new features in Firmware v2.3 was only the half of the truth. A feature advertised before the realease, the ability to subscribe/unsubscribe to podcasts from the player, was just added with it. It's very helpful when you want to get rid some podcasts from your player but always forget it when on Zune Software...
FYI I never pushed the unsubscribe button 
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[Thanks Adam ]