I use it all the time. I also use Rodinal and D76.
I use Tmax Developer primarily for Tmax 3200 and Ilford's Delta 3200 films, it was designed for pushing these films and it gives the best tonality with them of any developer I have used.
I used to use it all the time for Tmax 400, but when the new Tmax 400 came out (TMY-2) I began using D76 for that film. I recently shot some Tmax 400 that I developed in Tmax and liked the results and will be using it some more. I have not decided if I like it or D-76 best for TMY-2 yet. I use it diluted 1+7 for TMY-2, just as I did for the old Tmax 400. Tonality is nice, grain finer than I got with D76 1+1 but highlights block up more easily than with D76.
Tmax 400, Tmax Developer 1+7
Tmax 400, Tmax Developer 1+7
Tmax 400, D-76 1+1
Tmax 400, D-76 1+1
Tmax 3200, EI-1600, Tmax Developer 1+4
As to how Tmax Developer compares to Rodinal, it has finer grain than Rodinal. Tonality is different too, but that varies by film. I think Rodinal's tonality is gorgeous on Tmax 100, but Tmax 400 tends to have too little shadow contrast and the highlights have too much:
Tmax 400 in Rodinal 1+50. I have only done one roll of Tmax 400 in Rodinal so maybe by testing I can find a dev. time that would work better but my initial impression is that the tonality is harsh, which works for some subjects.