Pros
This position provides a ton of flexibility for those looking to develop a breadth of sales skills - proposal drafting, account management, financial analysis and value-based selling, contract administration, and pure sales duties. You facilitate most of the sales director's work, with the director providing final authority on pricing and strategy. You are essentially "shadowing" the sales director, and results may vary with different sales directors providing different approaches and account management techniques.
Cons
You are essentially the deal's "utility player." You are expected to learn a working knowledge of a lot of areas, but to learn none well. Ideally you develop sufficiently in one area to take on management of that aspect of the sales process.