The weight reduction claims are largely bogus. If you cut half an inch out of the middle of a bolt action you have removed mostly air, with two, maybe three ounces of steel. Any further weight reduction comes from elsewhere, such as a lighter barrel and lighter synthetic stock, not from a shorter action. Standard actions were already light enough to build a rifle too light to comfortably shoot, especially in magnum chamberings.
As for the shorter bolt throw, if you're really interested in saving milliseconds you should get a pump or auto. Smoothness of feeding probably has more to do with speedy reloading than does the bolt travel.
There never was any "need" for the super short, extra fat rounds but I have no doubt they all work just fine, I just don't see any special advantage to them.
New rounds certainly add to the burden of gun shops which already have 200 grand invested in ammo and don't make a penny back until it sells. They can't compete with Walmart on the common stuff so they have to stock whatever Walmart doesn't and that means the uncommon rounds which may sit on the shelf for years waiting for that one customer. New chamberings do sell new rifles, ammo, reloading dies, etc in the short term but after the fad has passed the store still has to stock the ammo for many years to come. Of course I'm referring to "normal" times, pre-Obama and hopefully soon post-Obama.
