I have it too. It's decent. I don't use it much, and I knew I wouldn't as it is a specialty lens. That's why I got this cheap one and not the twice as expensive 10/2.8 fish from Sigma for example. I could justify the purchase of the fairly cheap Samyang pretty easily.
The main thing for me with the Samyang fish is that it's a fun lens! If crazy perspectives and warped images are your thing, then go ahead!
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Canon DSLRs: 5D Mark III, 7D
Canon lenses: 17-40/4
L, 24-105/4
L, 24/1.4
L II, 50/1.4, 85/1.8, 100/2.8
L Macro, 70-200/2.8
L IS, 100-400
LOther stuff: Canon Extender 1.4x II, Canon 580 EX II, Canon 430EX II, Velbon Sherpa 600R
Apple: MacBook Pro 15", iMac 27", iPad III, iPhone 4S, Apple TV
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