Those were some of the advantages. There are disadvantages, too.
Might as well post those in all fairness (courtesy of studentdoc.com):
-Time. The MD or DO/PhD program typically takes 8 to 10 years to complete. By the time you're done with your degrees, the people you started med school with are finishing their residency. Some may even be on the faculty of the med school.
-You're not done. Before you can practice medicine or do research you have another 4-7 years of training. If you do a residency you'll be able to practice medicine; if you want to do research you'll have to do a fellowship. The alternative to doing a residency is to do a scientific post-doc. You'd be able to move into a faculty position sooner, but your pay would be that of a PhD, and you wouldn't be able to practice medicine.
-You're no more competitive than a single-degree job candidate. If you're looking for a faculty position in a clinical department, an MD/DO with a fellowship is much more appealing than an MD or DO/PhD with just a residency. If you're looking for a position in a basic science department, your doctoral degrees matter less than the quality of your research and your recommendations. In the end, if you're good you could probably cut 4-5 years off your training and still end up in the same position.
Admission Requirements
Admission to MSTPs is competitive. It usually requires good grades (3.6 or better), high MCAT (10 or better per section), a good GRE score (1300 or better), significant research experience (publications are a big plus), and strong letters of recommendation.