via ScienceDaily, a new survey of Sun like stars appears to indicate that the formation terrestrial type planets around such stars may be fairly commmon. The survey covered a range of young yellow stars under 3 billion years old and sought out tell tale signs of terrestrial planet formation, clouds of dust surrounding the stars. The warmer the dust, the more likely that accretion and collisions within it have caused planets to form.
"University of Arizona astronomer Michael Meyer led a Legacy Science Program with NASA's Spitzer Space Telescope to determine whether planetary systems like ours are common or rare in the Milky Way galaxy. Meyer and his colleagues found that at least 20 percent, and possibly as many as 60 percent, of stars similar to the sun are candidates for forming rocky planets."
The lower figure is arrived at by calculating the potential for "warm dust" near the stars indicating planetary formation to sustain itself as the stars age. The 60% number comes from a more optimistic viewpoint indicating that larger dust clouds would from planets quickly from the available materials, but it may take smaller clouds of dust longer to form planets. Meyer believes the true number is likely somewhere in between the two figures.