I think life is probably fairly common. Intelligent life very likely much less so. Even on Earth, intelligence is a solution to the problem of survival used by only a small fraction of organisms, and even among the organisms that use intelligence as a solution, that intelligence doesn't have to be at the level exhibited by a rather small number of tool-using animals.
But it's going to be a long time before we figure out whether intelligence is rare or not. I don't think SETI is the answer, since incidental transmissions (like TV and radio) only propagate out a few light years before they become indistinguishable from ordinary background radio sources. No, I actually think we'll ultimately identify other civilizations through advancements in optical and radio telescopes which will betray tell-tale signatures like pollution in the atmospheres of Earth-like exoplanets. That's still many years away, but eventually we're going to build large scale space-based interferometer array that will be sensitive enough to image continents and oceans on exoplanets.