I had no issue with them when I had a problem with a wheel, they gave sound advice and authorised payment for LBS to sort out. That was nearly three years ago before their UK service centre was going I think.
About a year ago, may be a little more, a friend had a problem with his Nerve CF when the bike was about 10 months old and after a short delay (less than a week) in communication which he did find frustrating, they replaced his frame and paid LBS to strip and reassemble. Total time from start to finish was about a month but as I think I have said before that is no different to other companies where replacement stock is not in the UK-Trek for example.
So a long winded way of saying our experiences were OK.
To put the reliability into perspective, amongst my cycling group there are currently 8 Canyon bikes, including a new Strive, and the above are the only warranty issues