My main camera for photos is my Nikon D7100. I'm happy with the Nikon D7100 for photos however for taking videos, its autofocus system is not suited for run and gun type video.
I purchased an A57 for Video since it has better autofocus in video mode than the Nikon D7100. I've also been using the Sony A57 for still photos more and more these days as I usually take it along for casual shooting where I need to take a combination of video and still shots. No point taking 2 cameras along.
I have a Nikon 70-200 F2.8 VRII lens for my D7100 and was thinking of getting a 70-200 F2.8 for the Sony A57. I have spotted a previous version of the Tamron 70-200 F2.8 without VC in mint condition for about $500 which I think is a bargain for a 70-200 lens. Given that the Sony body has built in Image stabilisation, will the previous non VC version of the lens perform well on the Sony Body? I've also read that the older version of the Tamron 70-200 F2.8 non VC version has slower auto focus. I would probably use my Nikon D7100 and Nikon 70-200 F2.8 VRII combination for sport photography or anything needing faster auto focus however, I would still need the Tamron/Sony combination to have autofocus speed that is acceptable for normal photography and for Video.