I use a 60D and have a Sandisk Extreme class 10 16G and a 32G card. I have never had a problem recording video.
Not all class 10 cards are equal and there are fake cards as well. If you want to speed test a card, put it in a computer with a good reader and see how long it takes to read or write a 2Gbyte file to it.... you will be amazed at the differences between class 10 cards....