Pros
Compared to non-pharmacuetical companies, the benefits are quite good. Also, being a major pharmaceutical company, you have the opportunity to sell some very high-profile, excellent products such as Plavix, Lantus, Actonel, Lovenox, and Taxotere. For someone trying to get some sales on a resume, it's a great opportunity.
Cons
The management is the number one downside. There is very poor communication from the top down, and in the case of layoffs/re-organizations, employees have historically be treated with extreme disrespect. I've also worked at another major pharmaceutical company, so it's easy for me to compare. The benefits are not as good. The pay scale for sales reps is also among the lowest in the industry. Another major issue is that depending upon which sales force you work for, you will be less happy. If you're selling in the Lantus/Plavix arena, congrats! You have great products with high market share and you sell the "urgency" of the disease state - these products save lives. However, if you're selling in the allergy arena with loads of over-the-counter agents, it's an uphill battle daily. Likewise, with osteoporosis and anti-hypertension, while Sanofi has solid products, there is a lot of competition, and if you are in an access challenged market like Boston or Minnesota, it can be very demorzalizing to reconcile the selling environment with the unrealistic expectations of upper management.