There are a lot of other good things about the projector as well: since it's a laser projector (the specific technology is called "pico p," and Microvision is looking to sell not just these retail units, but the tech itself to anyone willing to pay), there's no focal requirements -- you can basically point it at any surface shape, and it'll project in a visible way. It's a piece of cake to use -- just plug it into the iPhone and go.
There are enough issues that the unit isn't perfect yet, and not all of them are Microvision's fault. For one thing, that battery -- it only lasts two hours (enough to watch a movie, but not much else), and it basically doubles the size of the iPhone. For another, the capability -- Apple hasn't yet enabled developers to project screenshots or actual app screens from the connector port, so while this might be a great device for showing off apps to friends and business groups, no dice. And the price is still a bit high -- at $500, business users may be interested, but not many regular people will pay more than they paid for their iPod touch just to project pictures from it.
Personally, I think we will see projectors more and more -- eventually, they'll be included in a successful device (maybe even an Apple device), and consumers will enjoy projecting their favorite content on makeshift larger screens. But the technology just needs to get a little smaller, less power intensive, and a little cheaper. Microvision's projector will be available in the US in March, and you might even see the sales guy bring one around the next time he arrives at your company for a pitch.