Actually I just did a quick test and the 800RPM, just like it says, moves less air than that the SFF21E, but is way quieter. The Medium Speed SlipStream is slightly louder than the SFF21E, but moves more air.
There are other fans like Noctua and SilenX that are really good as well, but they are in the $15-$20 range. Cooler Master also has a 120mm fan that has excellent airflow for the noise:
Cooler Master Long Life Fan It's advertised at 19dBA and 90CFM.
I'd call BS on anything that has such high CFM with low noise. However, that doesn't mean this isn't a decent fan. I've compared it with fans from Noctua and SilenX and it definitely holds it own. For about half the price of the Noctua's, this fan is pretty good value also.