On Bungie.net if you go to your Gear section for your character you may see a button below your character entitled Gear Manager Beta. It is a pretty nice official manager, has drag and drop, the ability to select more than one item (with ctrl click), transferring from character to character, sorting, and the ability to see all items in one pane. Currently no option to transfer a portion of stacks, but I'm guessing that will come since it's already a feature in the current webapp/app. If you're in the beta give it a shot, or if you have questions let me know.