I have done numerous short sales successfully closing many. One of the most common questions I get during my listing presentation and explanation of the short sale process is " How will this short sale affect my credit score?". So, I am able to give you an actual testimony of one of my past clients who checked their credit score prior to their short and after.
This seller sold their home in 2010 with a short sale on the second lien holder only. The seller did not miss any mortgage payments but was able to prove a hardship, though. When the seller's started this process his credit score was 780 and her credit score was 730, now six months after the short sale was final and reported to as "legally paid in full for less than the full balance" his credit is 776 and her credit score is 637. So, this shows that yes, you can get a short approved without missing a payment and it won't always be a big hit on your credit score.
This is a real life example of how a short sale can affect your credit score but of course each situation is going to be different.
If you have done a short sale, I would welcome any feedback!!