I have more or less the same issue. I just changed the thermostat because the service engine light came on and the dealer said that was why. (They also wanted $500 dollars to do it!) After installing the new thermostat on the way home the car started upshifting a little hard into 2 and 3, but the downshifts into 2 and 1 are really hard. I don't know if the new thermostat is related in any way but since it occurred after changing it I thought I'd mention it.
Anyone have any ideas? My car is a 2002 330xi with 99k.