Making the best of the six month delay I figure I will put $10 or $20 in a jar each week and then when the upgrade comes out I'll get a 2.0 X III extender for my 500 and it will be almost "free."
Then compare the 5D3 with 500 + 2.0 X (1000 mm) vs my 7D with the 500 + 1.4 X (1120 mm) and see which one wins.
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