Hmm... I did try this myself and found the difference in mood to be quite dramatic - even with only one curve point eg. input: 224 output: 192 (although I normally use 2 curves adjustment layers).
Color has the most interest. I don't find the subject that interesting, the design is too chaotic. If it was simplified and maybe a subject to focus on, it might have more impact. Maybe a colorful bug on the grass.
Well, agains all expectations, i'm not that much for the sepia. I prefer the colors, but the B&W just gives out a different feeling, it's kinda colder or something...
Anyway these are awesome pics!