There are several posts ragarding this site. Some good, some bad. Just read through the seed bank section and make your own decision. As for yields, most seed banks/breeders exaggerate yields. Most use SCROG methods to establish a general estimate of yields per sq yard/meter. Yields are more dependant on the grower, and the strain also plays a role. I have gained better yields than some estimate, just as I have had yields that were not even close to what the seed distrubors claimed.
I have ordered from these guys many times now and have also grown that particular strain. I was growing indoors, hydro and although i didn't come close to that yield (finished up around 2lbs in a 2 meter square SOG) there was definately more potential in it if this was done outdoors with a longer veg period. You have to remember that the yield seeds banks put on the pack is in the most perfect situation, grown in big commercial setups under insane lights etc. If you take what they say as a guide then you should be fine.