I would say based on my experience at one top 10 b-school and having friends at other similarly ranked schools (top 3-15, not top 3), that starting salaries for MD/MBAs without residency are exactly the same in large companies as those with just an MBA. Don't know if they progress faster at the company though I somehow doubt it.
MBAs with significant medical experience can sometimes jump to non-entry level spots (e.g Medical director type jobs), but in general, that is rare in large traditional MBA jobs (e.g. I-Banking, Management Consulting, etc.) Exceptions might be found in areas like Venture Capital and start-ups where the ability to do multiple jobs can be more highly valued.
On the other hand, having a MD does make you a more attractive person on paper at a lot of companies (esp. health care companies) and will help you get your foot in the door to an interview that you might not otherwise get. After that it is up to you. Outside folks tend to think having an MD means you are smart (little do they know!) so you can leverage that to your benefit.