What's with the pre-meds posting threads here, and then being answered mostly by pre-meds?
This has been done to death. See "DO Disadvantages," a thread also on the first page of the Osteopathic subforum, for an honest discussion of what's probably the biggest obstacle you'd face as a DO.
As far as respect, my brother made a joke during a family dinner that I was "just going to be a DO." My aunt, who knew I was in medical school, then asked, "What's a DO?" That's an example of why people say it's less respected. Everyone knows about House, MD, and there was even that Newsweek article "Hero, MD," which was actually written about a DO urologist in the military.
I asked a friend who was applying to medical school the same time as I was if he was going to apply osteopathic as well. He told me he didn't want to just work with bones, so no.
And I once heard a nurse ask what a DO was after seeing it behind the emergency department attending's name. Two others also didn't know, and a nursing student then went on to explain that they don't like to give medicines. Meanwhile, nobody questioned his orders, and he was paid exactly the same as the other ED physicians. The lack of respect is typically just a lack of awareness, aside from the occasional goofball who assumes that going to an osteopathic medical school means you're dumber than all the kids who went allopathic.
The lack of respect from residency program directors, on the other hand, is something worth considering. And for that, I direct you to the thread I referenced earlier.