I like the "flatter" UI design overall, but I agree on the whitespace. Especially in Gmail. I wouldn't mind a flatter phase going through The Internets, as I think it's less distracting, but I entirely agree. Less wasteful display of data, please.

I would be interested in any info people may have as to whether such a large amount of whitespace does or does not improve user's understanding/use of sites. I like dense displays, but I'm also willing to learn how to use more powerful tools, as I value the efficiency.