I recently spent a lot (although a lot less than I could have) after bargaining down a dealer on a refurb P45. Altogether with a Phase Camera Kit it was less than twice what a Nikon D3X or Canon 1DsMkIII costs (which I sold for 1/2 what I bought it for one year after purchase). In the three years since I moved from LF to digital, I have lost a lot of $ on depreciation and finding out I personally can't use the Canon system worth a damn. Here are a few thoughts I have from the experience:
Medium Formal is probably worth it if you:
1-Are rich or make money hand over fist- buy new and enjoy!
2-If not rich or super lucrative, buy used or refurb, and don't be shy about the haggle. These dealers would rather sell an old back then wait for the next whale to walk through the door.
4-Want flexibility of use: like say by using a viewcamera, or a "plate" camera, or a homemade thing you machined in your garage.
5-Want your CAMERA to have shelf life beyond your sensor, and not just your lenses. I am actually pretty happy with the Phamiya and Mamiya glass, and imagine upgrading the back before the camera.
6-Like to take your time (or can afford to take your time) on jobs or making pictures in general. You can take Canon with a wide autofocus on the most demanding Architecture job, shoot a bazillion frames from all angles, and make passable work after having your assistant spend the weekend stitching and HDRing countless files. Or you can take a MFDB and a shifting camera, take twice the time and a tenth of the exposures, and have everything almost finished in camera, and totally finished in Capture One by the end of the day. Also you are more likely to get that beautifully simple easy-to-overlook shot.
7- If you Print big. Period. Ive spent a lot of time trying to make a triple stitch from a 21MP 35mm camera look like a clean LF exposure, and it just aint the same thing. It is different and easier and maybe better. But not the same thing. My outdated (and very ISO limited) P45 39Mp sensor just draws an image with a clarity that I havent seen with a Canon or Nikon.
8- Can't Stand the 2:3 ratio and wonder who the hell ever came up with it. Very simply, I don't make prints in a 2:3 ratio, therefore with the Canon I either had to crop or stitch. This is a particular and nitpicky bugaboo, but hey, we've all got problems.
Do not go MFDB if:
1-You want lowlight capability, at least until the P65+ comes down to a reasonable price point. But by then Canons and Sonys and Nikons will be able to shoot in pitch black and see through walls, so you still dont want to mess with the finicky DBs.
2-Size Doesnt Matter. Of the print, I mean.
3-You want speed, and the ability to get that impossible-to-catch shot. I pity the sports photographer that ever brings a Phase kit to shoot a tennis match. Or to his kids soccer game.
4-You are cheap. I'm actually pretty cheap. But I needed what the DB could give me, and didnt need the good stuff from Canon. However, the Canons of this world will ALWAYS have some hi-end product that will give ya a little more for your buck then Hassy Leaf or Phase are willing to give, pound for pound. Its simple economics and the higher competition & volume in the larger 35mm DSLR world.
These are just my opinions after giving Mr. B and Mr. H way too much of my money. Hope it helps.