I have 30,000 miles on my '09 and there is TSB 09-11-5 that I had done which addresses a hard downshift into 4th gear at highway speeds. I only experienced this twice and it was within the first 10,000 miles. Never had time to take the truck in so didn't take it to the dealer until about 28,000 miles and they updated the PCM.

I would think that this update to the PCM would already be done in '10 trucks but maybe not.