I have never found traffic to be useful unless the freeway had already been backed up for quite some time and even then it was sketch at best. I used to drive with my Garmin with traffic on and more than once it has rerouted me into traffic instead of away from it. (I used to commute from the East Bay to San Francisco for work and often go to San Jose/Milpitas/Union City to visit friends.)
I recall driving up to a stretch of highway that was yellow (a slow down) on the GPS and the road being clear with no traffic. All of these occurrences has bred distrust between myself and Garmin's traffic, so much so that I consider it a gimmick and do not rely on it.
That said, I ordered the 2455LMT eBay deal last week so I'm waiting to see if Garmin's traffic system is any better (I doubt it.)