Questions For Experienced Short Sale Investors

I wanted to ask all of the experienced Short Sale Investors (those that buy & sell to end buyers via a back-to-back closing) what are some typical profits you all are seeing in this market? I would like to focus on higher end luxury homes, has anyone been successful negotiating these type of deals at a discount, and what are typical profit margins? How difficult, and how long are short sale deals taking to close, are some markets quicker than others? I mainly wanted to get an overall feel on this strategy in today's market before I invest my time & resources in Short Sales. Any feedback would be greatly appreciated!