For starters, while the housing's the same, the $549.99 GP2 integrates an iPhone/iPod dock, which is a big deal. It also features 1,280x800-pixel (WXGA) resolution and native support for 720p video.
BenQ also says that it has improved the interface and now offers an optional battery pack that will power the unit for 3 hours at half brightness (100 lumens) or 1 hour at full brightness. Two built-in 2-watt speakers deliver sound, and a remote and carrying case are included.
As far as memory goes, there's 2GB of onboard memory, and like its predecessor, the projector can read several different file types stored in internal memory or on a thumbdrive or SD card. (See full specs here).
The GP2 was scheduled to ship in December, but right now it's listed as out of stock on BenQ's Web site so it's unclear whether it actually shipped. We'll be checking it out at CES and will let you know if it's really worth $550.