Yes I love TMAX 400. Man I hope that whoever buys Kodak's film division doesn't mess that up! I shoot it in my 4x5's, Hy6 and F4. It's really nice in the RZ as well!
RE: Mamiya DF... my hunch is the viewfinder black out is all about waiting for the mirror movement vibrations to die down. Digital backs with higher and higher res probably force longer wait times so even though they've revised the body, they can't do anything about the black out - probably getting worse if anything. I have no idea what Phase/Mamiya have up their sleeves but the new camera body has been said to be in the works. I sort of hope for them they ditched the DF all together and went with something new.