The great thing about these clamps is that the I beam makes them very stiff, they will not bend like pipe clamps over a long distance.  They also have crushing power, I think they have 7,000 pounds of force, compared to 1,000 for a Bessey parallel clamp.  You can literally crush wood with them, as you can with a vise.  The crank makes it easy to tighten, they tighten very fast.  Biggest flaw I see from experience is that they have a small clamping face...this makes it less effective when clamping an "edge" like a cabinet or door.  A Bessey or Jorgensen parallel clamp has a much longer and even grip on the edge of wood...down at least 5 inches or so.  Then again when you need a small clamp, as when clamping a small table leg...this is the best choice, the parallel clamps are too big.  So these are best for powerful clamping of small spots, or strenth and straightness over a distance, such as a door, where a pipe clamp will arc and bend your wood out of alignment.  You can always spread out the clamping force with a piece of hardwood, but then you need 3 hands to hold it all together.  You can use these with steel, where a Bessey wouldn't even be considered.  Wood screw clamps, like the traditional Jorgensen, are best for really long edges of a foot or so, or small piece where not much force is required.  Then again you don't want to squeeze out all the glue either.  So you have to match the clamp to your work...no one clamp does it all.  Another use: when first setting up the wood, squeeze the pieces together with this clamp, as when gluing two pieces (as in making a door with a rail and stile) with a biscuit or biscuits.  This powerful clamp will act like a vise and pull them together, it's easier and quicker to get great force out of this clamp than any other kind of clamp.  Then use a Bessey or other brand to hold it evenly.  The "vise" action of this is unique and sometimes the best option around.  I have every brand of clamp and many antiques but when this baby does its thing there's no substitute for it.