Vicky Cristina Barcelona was... not a complete waste of time. (Note: Arguable spoilers follow; if you are planning to see the film and don't want any plot elements given away, don't read this.) There were fun and even moving bits to it, it was really enjoyable visual composition, but the movie did not hold together. It did not seem like the filmmaker's heart was in the project.
The central problem I had with the movie was the voice-over. The narrator was obviously, audibly bored with the story he was telling. Every time he started talking I tuned out completely. Ellen suggested the narrator was playing the role of Allen's character in his old movies, which sounds right -- but Allen's character being bored with his own life comes off as jaundiced and world-weary; whereas Allen's narrator being bored with the story he's telling just comes off as lazy.
Also lazy: not bothering to develop the character of Judy, the older woman who is trying to warn Vicky off of getting bogged down in an unsatisfying marriage. The first conversation she has with Vicky was really moving and sympathetic, and seemed like it had the potential to form the emotional core of the movie; but apparently Allen was not interested enough in the story he was telling to develop that any further, once he had the plot element set up he lost interest in the character.
So... not a great movie. Fun and pretty, though! The high points for me were four actors: Rebecca Hall, Patricia Clarkson, Javier Bardem, and Penélope Cruz. These four are just splendid, poetry in motion. Watching them move around through the streets of Barcelona is an excellent way to spend an hour and a half.