> Is there any actual benefit to this? Will using one have a noticeable impact on either the individual lifespan of the shrimp, or the long-term survival of the ecosystem?

It depends entirely on your current method of aerating your tank. 

If you aren't adding oxygen to the water (usually by bubbling air through it) then the answer to both questions is yes - any aeration is better than none.

If you are already aerating your tank enough to meet their needs, then there's no additional benefit to using this method, other than ease of use if that compares more favorably to your current method.