I watched it free with commercials at Hulu, where it's currently behind a paywall.
Senses of Cinema calls it " a remarkable work". Slant Magazine gives it 4 out of 5 stars. The NYT concludes, "The virtual orchestration of graphic detail that Antonioni has managed here, the interesting blend of the human idea with pictorial chic, is affectingly complemented by an excellent musical score."
BFI calls it "one of the most disturbing films about life and relationships in the mid-20th century". Empire Online says, "Michelangelo Antonioni has managed to make a film about the humdrum and make it simultaneously tedious and wonderful." It's included in the book 1001 Movies You Must See Before You Die.
Rotten Tomatoes has a critics score of 92%.