Originally Posted by Venturi 
Interesting you say that, because the only difference (in post processing) between the two copies I posted is I flipped the "Treatment" switch in LR2 from Color to Grayscale on the 1st one.
This could still result in over- or under-exposure depending on how the grayscale is calculated. I do all my mono conversions using the Black & White Adjustments layer in PS, since one can individually tweak every channel.
Check out the detail in the petals. I do see a tad more in the grey image, though both are blown, a common problem with flower shots. (As I well know!)