Pros
The best thing about being a MDP is having the MDP community. Now that every MDP starts in client support, you'll instantly be placed on a team with 5-10 others just out of college. This makes for a fun, social work environment with frequent happy hours and weekend bonding. It also helps that no one on support is allowed to work more than 40 hours/week. (The fact that the 'social' aspect of the job is my biggest 'pro' should be taken as a double-edged sword).
Cons
Unfortunately, the MDP is often not what it claims to be. It's not uncommon for someone to get stuck on the phone for 12+ months because 20+ MDPs are all interviewing for the same 3-5 positions. Do not believe anyone when they tell you it is a 'rotational' program. The only rotational aspect is the fact that about 25% of MDPs leave each year. Additionally, as a MDP, your pay will be significantly lower than were you to work a similar job at a different company. Of course, this salary cap is lifted upon graduating from the MDP program, but that puts you at about 2.5 years on the MDP salary (think 50k starting, plus a 0-6% increase twice annually). This salary is certainly fair when on client support, but quickly loses its appeal when accepted for a (real) job.