I have a set and they work well.  I don't know that they give any big advantage over regular handles, but they will keep your hand from getting stiff after a long casting session. 

Chris.

I have a set, and they are very good, well made, and work as advertised.  Whether they are useful to you is a matter of your circumstances.

The things I don't like about them are they are heavy and slower to use.  I have a damaged left hand that doesn't operate them very well.  It is easier on my hand to use a regular mold.

However, they have three main advantages:  One, they are great for someone with limited strength in their hand/arm, as they can be filled and then set down.  Second, they hold the mold halves together better so you don't get slightly oversize bullets that weigh more.   Third, they can be used in tandem with a second mold/handle set, you fill one, set it down, fill the other, set it down, pick up the first, dump the bullet out, refill, set down, repeat.  I've heard some shooters that do this say it increases their speed overall.

If you have any problems getting oversize bullets or with fatigue in your arm casting, then I would highly recommend them.  They are the best solution out there for those problems.  If you can cast perfect bullets now without getting tired, they're a solution in search of a problem.   

dave

I also have three sets and I love them they give absolutely the same pressure when closed each time. Also if you get a tiny blob of lead on the mold face you can feel it when you close the mold the next time. The one drawback is they take some getting used to. There is only one handle and its round so you really have to grip up when you turn it over to fill. You can make it easier on your self if you take off the round wooden handle and replace it with a cut-down hammer handle the oblong of the hammer handle makes it easier to hold.

40 Rod