Fertile Eggs. Shipped versus Non-shipped

I have heard a lot about how "handling" of fertile eggs can cause a reduced number in the eggs actually hatching. Aside from the egg actually cracking or breaking why would you have a reduced number of hatched chicks? I have heard the following reasons.
1. X-ray machines "killing" the egg. Not sure about this one. I have my doubts.
2. Shaking the package. If this was true, then wouldn't all the eggs be duds? They all get shaken.
3. Temperature. Ok, here I can see being a good reason. If temps get too low, (or too high?) then I
     would guess the result would be a "dead" egg.
4. Delayed shipment. Most eggs if shipped priority should be delivered in 2 to 3  days. Unless the
    sender didn't ship the freshest egg, this really doesn't seem to be much to worry about.

So, all said, if I ordered a box of eggs that were hatched the day or the day before they were shipped, they didn't see extreme temps and they were never jostled or x-rayed I should expect the same percentage of eggs to hatch compared to me actually picking them up from the breeder and waiting a day or two to set them.

I know there are many factors in what makes a good hatch. I guess I am just trying to see if buying shipped eggs is THAT big a risk all things being equal in the hatching process.

What has been your experience?