Two new warframes, the poisonous Saryn and sonic Banshee, have been added to the game along with a few new weapons and melee stealth attacks. A new training challenge and endless defense mission have been thrown in as well. The game's mod system has undergone pretty significant changes. Weapons have see tuning and balance updates, and a large list of fixes have been added. Check out the forums for a full list of changes in Update 7.
Thanks to intrepid internetter Ken for the tip.