Ray,
I've worked in the oilfields as a driller for most of my adult life, and I've spent a whole lot of time standing on a diamond plate floor, which can't be much different from concrete, as far as comfort is concerned. Ninetyfive percent of the people I come in contact with on rigs wear either Redwings or Wolverines, Comfortforce or Durashocks. I got a pair of Wolverines as a safety award once, and they split along the soles (not the seams, the leather) in about four months. Redwings last longer for me; I've had my current pair for about a year now, and they are still holding up. I buy my boots a little big, put a Dr. Scholl's insole in them, and wear two pairs of thick socks. The biggest difference I've noticed in my standing comfort came when our toolpusher ordered us a mat like the cashiers at Walmart/the grocery store stand on. It's about an inch thick of some kind of soft material, and it makes a hell of a difference.
One of my good friends is on his feet all day at a local saw mill, and he swears by Dr. Martin's boots. I've worn Doc.'s for years as casual wear and can attest to their comfort, but have had questions about how long they would hold up in a working environment. My friend has been wearing the same pair to work for about four years, and he wore them as everyday boots for a couple of years before that. The next boots I buy for work will be Doc's.
edited to add: I weigh about 280 lbs., so I probably need more cushion that most people to keep my feet from hurting, although my 280 is spread over a size 14.