i was at petsmart today and i notice they were selling Hagen CO2 Natural Plant System. Does this stuff really work?

I used something similar for a while and I noticed a difference - for the better:

http://www.aquariumguys.com/co2fizzfactory.html

The one I used did not require sugar which is a little easier but the gas chamber was such simpler - (I don't know what the bubble counter is for on this model) - the chamber on the Hagen looks like it might be able to sit outside the tank? If so, that would be nicer than the Fizz Factory one which was suction cupped to the inside of the tank... But I definitley saw a noticeable difference in the plants, whihc gre much faster and bigger, when I used to CO2 once a week.

thanks graham. i went out and picked up the hagen CO2 natural plant system. the canister sits outside of the aquarium rim and the bubble counter is mounted inside the tank. i'm hoping my swords leaves will regrow after being chewed up by the goldfishes.