I bought the Legend Hcx last week and upgraded to 2.7/2.6 a few days ago. I also did the hard reset (it's called hard, because it's hard to accomplish ). I haven't seen any drift yet. Yesterday I did a hike on a cloudy day in a dense forest. The tracklog followed te trial almost exact in mapsource, although we where moving very slowly because of my 2 year old daughter....
Maybe I'm not the best reference, because I just got the Legend and do not know if the drift would have happend with the lower firmware version.