The 70-200 is a different class of lens. I've never had to repair mine but I have had to repair my Canon 15-85 so I guess that's a wash. lol
I did drop my 70-200 onto a hardwood floor and knock the OS out of whack. I sent it to Sigma to get an estimate and when I called 5 days later to see what it was going to cost, they said they fixed it under warranty and shipped it back. It showed up on my porch later that day so I'm a happy camper.
I don't think it's soft at the long end. I think it's a tad soft at f2.8 compared to the Canon MkII but I'm OK with that. "Soft" is a relative term and if the Canon wasn't sharper I'd be really surprised given the 2x price tag. At 200mm I've noticed that the actual magnification is slightly smaller on the Sigma compared to the Canon. I can't say for sure how much but when you place an image side by side at 200mm you can see the difference. It isn't a lot but it is noticeable.
A independant magazine about canon cameras, stated that the Sigma 70-200mm OS, is around 180 - 186mm, and that the canon 70-200mm f2.8 is only a tad faster and slighty sharper, in the real world. And this lens is better value than it canon counterpart (Sigma $941 compared to canons $2225).