This really depends on the individual(s). For me, at the rates I was offered when I purchased my home, a 30-year fixed seemed like the best choice with the option available to pay down extra principal at will. In effect, it allowed me to finance at a more comfortable price in case of a downturn, loss of job, etc., but still be able to speed up the process when times are good.
With interest rates as they are now, I'd suggest getting into as short of a fixed-rate mortgage that you can. Pay off what you can while interest stays low, and hope that the eventual rise doesn't affect you by staying fixed.