We’re almost certainly alone. If you want to play a numbers game this is the link to do it with, it’s a Drake’s Equation calculator.
None of the values in Drake’s Equation is actually known, so there are no wrong inputs. But trying to input reasonable numbers I come out with less then ten alien civilizations. Then stir in factors Drake didn’t consider, such as the density of stars in a given area of space (higher density areas being more subject to radiation, gas, and gravity interference with each other, remember we are out in the galactic sticks ) and I conclude it’s lucky we ourselves are here at all, much less competitors.
http://www.seti.org/site/pp.asp?c=ktJ2J9MMIsE&b=179074
Each to his own and with all due respect to Drake, the universe is a big place and different organisms live under different conditions. The one flaw that I’ve heard about his equation is that it’s roots are based on the Milky Way, which is only one of many many galaxies. What exists here and what truisms are known in this galaxy do not make it so elsewhere.
“Frank Drake’s own current solution to the Drake Equation estimates 10,000 communicative civilizations in the Milky Way. Dr. Drake, who serves on the SETI League’s advisory board, has personally endorsed SETI’s planned all-sky survey.”