Yes the image is definitely soft. You can see the progression of the depth of field over the photo with the sharpest point being on the Canon F1 (at least to my eye).
I think you've got some blur with the cause most likely being mirror slap. I'd be intrigued to see the same shot taken on a good tripod with mirror lock up and a cable release. If it was still unsharp then you have a problem.
I have a Pentax 645 IIn with 45-85 mm and 150 mm lenses. I find it a brilliant camera and wished I bought one much earlier. I regularly print out at A3+ and have had excellent results.