See: http://www.eisa.eu/awards/3/photo.html
Quoted:-
"With the introduction of the Pentax 645D, the medium-format market has gained a much anticipated and highly competitive member that offers exceptional image-quality and handling. The 645D is a joy to use in the field, and although it is big and somewhat heavy, its ergonomic grip, large viewfinder, fast and accurate autofocus, and well-made controls make it perfectly usable without a tripod. With its 33x44mm, 40-million-pixel, Kodak CCD-sensor it is a landscape photographer’s dream, creating absolutely stunningly sharp and detailed pictures with very attractive colours and a huge dynamic range. As a serious photographer’s tool, the Pentax 645D is second to none."
Anyway, the 645D is something that completely out of reach for me. It is not only for its price, but also for its size and weight of the system. Not even to mention it is not compatible with the Pentax K-mount, which is where my love to Pentax deeply associated with. I hoped that there is a Pentax 135 FF, but there is still none in the foreseeable future.
Related:-
Very Old Question: Will there be a Pentax Full Frame DSLR?