The pro model 'upgrade' is very cool and makes R-4 deck much better over previous 'prosumer' model in my opinion.
However, what keeps me from wanting one is the lack of 88.2K sample rate.
In my mind, this sampling rate is needed so that recordings can be made for both high definition DVD--Audio AND be most compatible with 44.1K conversion for CD with minimum artifacts.
So far, 744T is most affordable 4-track with 88.2K sampling.