Originally posted by Alex645 The review on that site opens with "The first and so far only consumer weather sealed telephoto zoom" which makes me wonder how they categorized it this way if it is the only lens with those features. To me the only reason to call it consumer grade may be its affordable price or arguably the speed of the AF and f/4-5.8 aperture.
It depends how you define 'consumer'. Mostly gear is split into consumer, professional, and stuff that's somewhere in between. But the HD DA 55-300 WR is definitely not a professional lens. No constant aperture, extremely slow and noisy autofocus. Not very sharp wide open at the long end, should be stopped down to f/8 for good sharpness.
Yes, it is a very good lens for the price, but it is not a professional grade lens. The HD DFA 150-450 is. From a professional grade lens one expects impeccable build quality, very high image quality wide open, snappy AF etc. The HD DA 55-300 WR is a very, very good consumer lens.