As an OWNER and USER of a H4 I can tell you I think TF is one of the major selling arguments of the H4/5 and it really works well when you use it right.
I sold my MF system because my Mamiya's AF focus was just not compatible with my sloppy way of using a camera. So I'm happy to hear that Hassy keep making theirs better. In fact I hope to pick up a used H4 once the prices fall (another 2 years?).
At the moment, I am using Canon gear to take portraits of my kid in available light, and the big problem is *quickly* getting accurate focus while preserving composition The image below is with a $250 kit composed of a geriatric preowned 400D and a 50/1.8, at some horrible ISO that would be impossible with an MF system, and it is *manually focused*.
I've moved up again from the small Canon because I like AF, and I got a junkyard 1Ds3 which by using the my old 135/2 gives me the same results as the Rebel, with fast lowlight AF, at 10x the price
However, the consumer Canon probably cost me about 1% of a new MF system, and I'd say it still has better autofocus than the Mamiya.