The only down side of those weapons was the time and labor involved in refilling the reservoirs. If you include the recharge time they were probably not much faster in rate of fire then the flintlock's of the day. To bad development of this style of rifle stopped if it had continued we would probably have a much bigger Air Rifle market with a whole range of calibers that price wise would be right on par with some of our favorite powder burners.
Now if we could just get Beeman to produce replicas (with necessary mods to ease production) for the open market that would be way cool.