Do you need a motorcycle license in Michigan to operate a 150cc scooter or will a driver's license suffice?

Yes, from the research I have found online (im looking to buy one myself) any scooter/moped over 50cc requires the motorcycle endorsement, insurance, and a helmet in Michigan.

Source:

http://www.moped2.org/laws/Michigan.htm

**Yes you still need a motorcycle license but I have more accurate information from michigan.gov:

"A moped has an engine displacement not exceeding 100cc, no manual gearshift, and is capable of no more than 30 mph on a level surface. If it does not meet all three of the listed requirements, it is considered a motorcycle."

source: http://www.michigan.gov/sos/0,1607,7-127-1627_8669_53329-212754--,00.html