I'm interested in this lens for video. How do you think Sigma's OS (Optical Stabilizer) performs against Canon's IS (Image Stabilizer)?
The Canon one is definitely better than the Sigma you can find on their EX lenses. Really smoother and quieter.
Moreover, stabilisation is a fragile part of the lens. I'm not talking about the reliability of the "new Sigma" but on my EX (which was quite their top of the line), the stab broke down one year and a month after the purchase (intensive daily use)... And on their EX 120-300, it was the noisiest i've ever heard.
I've been a proud and very satisfied Sigma user for a year and a month (I find that their last 70-200 is optically a bit better than my Canon 70-200 2.8 IS I). Thinking that issues only happen on other people's gear. I'll never buy one of their product anymore.
When your 1000€ and more Canon gear needs to be fixed, you can get a replacement one until you get back yours (usually a few days or a week later). Sigma needs 2 or 3 weeks and about 250/300$ to fix it and you're on your own during this time.