Sept. 2006: We bought a 1200 for the UGJ system in our 40 gal tank after reading the great reviews here. We haven't been disappointed. The price was great (<$19 online).
With a little filter media in it, it moves and filters the water really well. (We also have an external canister, but have found that this powerhead works so well that we don't have to do the "full clean/change" on the canister as often).
It is super quiet, except it starts making a slight "tapping" sound, which signals to us that it is time for us to change the filter media. In our system, this happens about 1X/week. Other than that, it is noiseless,the fish enjoy playing in the currents/jetstreams and the bottom of our tank stays relatively clean.
We plan on adding a 75-90 gal tank to our home in the near future and we will definitely be using this brand when we build the UGJ system for that tank.
Update 6/2008: Still going strong and highly recommended!