I find the tomtom service pretty flakey all the time. I do about 20k miles every year, mostly on motorways, and it's nice when the live traffic works, but I find that it fails quite often. Sometimes I don't notice, like a couple of weeks ago when it took me straight into 45 minutes of jam on the M25. Once you're in, it can't find a way to avoid the traffic because you're already in it, so you have to turn off out of the traffic and then search for a better route.
I think I hate tomtom almost as much as I hate Bill Gates.