the early demo videos of their 5gh/s miner was actually running at 5.8-6 gh/s, and can be firmware overclocked to 7gh/s for 100$... so i imagine that their 50gh/s will run well above 50gh/s. (the hash ratings are a minimum, i believe that the specific number depends on the chip quality (being more or less prone to overheating) some chips can run faster than others, but even tho "lowest quality" chips will meet or exceed the minimum hash rate)

that said, they are currently shipping orders from June 2012... (except the 5gh/s miners which currently shipping orders from oct 2012) they have a lot to catch up on. supposedly everything ordered so far should be shipped by the end of September iirc... but if u just ordered yours then it wouldn't surprise me if it was Oct or Nov when u actually get your unit. BFL is pretty awesome at claiming to be on a certain timeline and then missing it completely.