i actually thought it was a pain in the ass when they started incorporating the attribute editor in the interface... when i first started learning maya it always opened in a different window... but that was around maya 2-2.5, and i really have no idea when they changed the options, but it's annoying so i've always changed it back to 'open in new window'... i feel badly for those that didn't know this was an option or have become used to the attribute editor being attached to the interface(and shrinking the viewports).