I've never used them - considered them to be a waste of money. What are they for? - to use your hunting rifle, be it a .30/30, .308 Win, or .30/06 for long range varmint hunting.
The ballistic specs tout muzzle speeds of the 55gr. PSP in the '06 exceeding the .220 Swift - flatter shooting BUT - in order to meet the requirements, accuracy is vital. Over the years, I've read of one .30/06, out of perhaps 15, that produced less than 2" groups at 100 yards, and that was back in the 1970's when they first came out. 2" at 100 is over 4" at 200 and probably over 8" at 300. What good is that when the chest cavity of most varmints is smaller than the 'potential best grouping from your rifle.

If you want a good varmint load from your '06, buy some 125gr. TNT Speers, 130gr. Speer BP's or 125gr. Sierra's and work up a 3,300fps load. These loads are accurate and are also devistating on vermin. If you want to save pelts, use a 150gr. FMJ at about 2,800fps. Learn to shoot them at all ranges you will be using them at. Even though they aren't doing 4,000fps, they'll still give a flat enough trajectory for shooting vermin at out to 400yards.