I bought one last year.
The bike was 6 weeks late arriving, and then it arrived with brakes that hardly worked. I contacted Canyon and they said I could take it to my LBS and they'd cover repair costs up to £20.
The LBS couldn't work out what was wrong so Canyon asked me to send the bike back to them.
This meant more time off of work to be around for collection/re-delivery so I told them to just refund me.
As has been said, for value they're hard to beat. If you look at the prices, you're really getting the frames for free!
I just couldn't be bothered with the messing around, so went and bought something I could swing a leg over before parting with the money.
That said, I would consider buying from them again, but I'd have lower expectations
Hope this helps!