Pros
I started at Cbeyond (now Birch Communications) with no sales experience, and left two years later with prospecting, presenting, and closing skills, an extra layer of skin, and the confidence that I had become a strong salesperson. The experience of walking in to 50 businesses per day every day (70 during training) with the intention of closing a deal at every location is one that sends the majority of employees packing within 3 months, but it is an experience that is a sort of badge of honor for anyone who can make it at least one year. Basically, you will toughen up or you will quit, and I can honestly say that this job toughened me up and made me a better salesperson. There is also good training on giving an effective sales presentation that I have carried with me to this day.
Cons
One of the worst aspects of selling that I encountered during my time was poor reputation and online reviews, based on the aggressive sales approaches of some managers and salespeople. More importantly, the push for sales sometimes led to poor recommendations that left very unhappy customers, who had to fight to get out of contracts they no longer wanted to uphold. Now that Cbeyond has been bought by Birch communications, perhaps these issues have been addressed, but I would look into it.