When reading the introduction text as well as looking to the samples, I am not sure if it would not be better if dpreview takes the hands off a medium format camera, no one buys a 645D to take just snapshots. This is really not the main usage of such a camera.
It does take a bit more effort to take a photo with the 645D than with a P&S snapshot camera.
In regards of weight, the 645D is similar to the D3s and no one asks if the D3s is practical to lug around a whole day. On a personal note, having both D3s and 645D, the 645D seems to fit better in my hand and shoulder and arms hurt less after one day with the 645D compared to one day with the D3s.
I added a few photos in full resolution to http://www.pbase.com/tcom/645d
00112233: Pentax 645D body is 156x117x119mm and weights 1480g. incl. batt.Canon EOS 1DX as announced is 158x164x83mm and weights "TBC"Now, to find out what TBC is we can assume that physically has the same type of construction and materials as the EOS 1D Mark IV which is smaller and weights 1230g. incl. batt., the 1DX will then weight more, specially if we include the wireless file transmitter and the GPS receiver. The difference in weight between the 645D and the 1DX will become very small indeed. So I wonder who is going to have pains in shoulders. Fortunately most professionals have assistants that help carrying equipment!
I do have the 645D and it has no LiveView.
@sdyue: the 1DX is not out yet, the 645D is available since over a year. And as the 645D features a CCD sensor, it does not have any LV.
It would be good if dpreview could test the camera with the FA645 75/2.8 which brings out much more details than the DFA645 55/2.8 kit lens. I do have a few samples under http://www.pbase.com/tcom/645d