When this pump came on the scene, it was a game-changer. With tubeless tires quickly becoming the norm, the ability to seat a tubeless tire bead onto a rim without the need for a powered air compressor is a function that a growing number of cyclists have come to desire. The high-pressure auxillary air chamber was successful at seating all but one tire/rim combination we threw at it. To be fair, this pump's main competitor in our test, the Topeak Booster was denied as well.
When used as a portable compressor, we have few gripes. It takes an average of 53 pumps to charge the high-pressure chamber, only slightly more than what the Booster required. The Flash uses a bit more plastic than we'd like to see, especially given the high use we anticipate from loaning this pump out to friends. Our main gripe comes when this pump is used as a traditional floor pump. When the hose is attached to a valve, air flows out of the tire and fills the pump. The tire is robbed of a huge amount of air which translates into more pumping. It's annoying.