The biggest difference that I see is the text(to be expected, JPEG's aren't famous for thier excelent text handling). And some of the shades and shadows seem different though part of that may be how my lcd monitor is tilted(doubt it though cause it doesn't look that way if I just view two of the same at the same spots on the screen).

Anyways I have played around with a few of your earlier ones as well, and it appears that however you do the dreamy effect it doesn't utilize the features that png has over jpeg(or at least not enough to make a big difference).