Anyone using a new model Sigma 12-24 on FX?

I'm thinking of getting an UWA zoom and was looking at this lens.  I have an old version of this lens that doesn't cut the mustard for anything other than just abstracts or snapshots on today's FX cameras. I've heard that the new model is much better than the old one, but would like to see your comments, especially if someone is using one on a d800.

thanks

Kerry

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my gallery of so-so photos
http://www.pbase.com/kerrypierce/root