It IS a really great duster and it IS very useful for a variety of jobs. It is NOT a replacement for canned or compressed air. Why? First of all, it gets HOT, especially when you use any of the flow restricting attachments. Both the body of the duster and the air it expels get very hot with prolonged usage, although no duty cycle is specified by Metro. Secondly, there are limitations to the amount of pressure it can generate, especially when you use the provided attachments. Compressed air, on the other hand, can be forced through a very small opening (like the straw included with canned air), allowing you to spray out nooks and crannies the DataVac simply can't get to.
Is the DataVac worth getting? Yes, because it's good for big jobs where you need a large, continuous quantity of air that would otherwise mean blowing through cans of air rather quickly. In that sense, it will cut down on the amount of compressed air you'll need to buy, not eliminate the need entirely.