Sorry to hijack this thread, but I have been searching for info on the 55-300 and 70-300 and this one came up and has lots of useful info.
I would also like to upgrade my Tamron 70-300 for similar reasons (poor IQ, slow autofocus etc) and would like to get one of these lenses. In perfect world, I would go for the 70-300 but am not sure my budget would stretch that far, am also worried about the weight of it on my puny little arms
Before I start the saving up, I just want to ask if the 55-300 (and 70-300) compatible with my trusty D50??