I have. Went Vancouver -> Kuala Lumpur on them, routed through Taipei. Granted the flights are cheap, but there's a reason for that. I wouldn't recommend them, and can say they're the only airline I've ever flown which I will now actively avoid. Then again, you might get lucky with a newer plane.

Everything was fine, had my own personal TV with loads of movies, and the food was fine. Then again, I expect airplane food to be shitty, so if it doesn't make me vomit, I figure it's pretty good. You may have different standards. Problem was the plane was quite old, and the seats extremely uncomfortable. It's the only flight I've ever been on where I've had to sit on my pillow, because my ass was getting numb. Not good for a 12 hour flight.

One good point with them though was, I changed the return date of my ticket, and surprisingly, without charge! With most airlines it's around a $50 change fee, plus the difference in ticket price, which is always more than the ticket you originally booked. I was expecting to pay around $300 or more, but it was $0.

PS. I remember doing this, Google the track record of airplane crashes based on airline. Air China is one of the top. They have a horrible track record. If I remember, Cathway Pacific has the best track record.