I did not have the chance the compare the old and new versions of the TAT2 but I had the TAT1 and TAT1 M2 in my own system. Both TT were set up by Ana Mighty Sound and were fitted with the same cart. I had the TAT1 for several weeks before swapping back to the TAT1 M2.
The evolutions of the TAT1 M2 are: a new platter, a redesigned air bearing and a new motor. The differences are subtle but clearly audible. The TAT1 M2 has more bass with a subjective feeling of an enhanced pace and rhythm. I would believe that this is due to the combined impact of the new motor and the redesigned air bearing.