I was looking at moving up from my 500 f/4L to the 600 f/4L II but the "lighter" 600 II would weigh as much as my 500 and I really want something lighter so decided to go with the 500 II.
Then I didn't win the $325 Million Powerball last weekend
EOS: 7D (2, 1 gripped), 50D gripped, 580EX II + CP-E4
EF: 500 f/4L IS, 100-400 L IS, 70-200 f/4L IS, 28-135 IS, 1.4x TC II, EF-S: 15-85 IS, 10-22
5D3, 17-40 L, 24-105 L, 24mm TS-E II. S100 p&s