Do you suppose that the French heavy cavalry's difficulties in 1815 were much different from those faced by French cavalry at Minden (or even at Agincourt, for that matter)? I suspect that any cavalry will endure difficult going when confronting anyone else's unruffled, prepared, and properly disciplined infantry. Might this be a timeless challenge?!
Yet, I am curious about what factors might be identified to distinguish massed cavalry handling in the Revolutionary-Napoleonic period from that in the previous major European conflict, the Seven Years War. Yes, as Kevin has pointed out, the earlier organizations did not embrace a Napoleonicly-patterned reserve cavalry corps of some permanence, or even permanent divisions, but still seemed capable of a high degree of flexibility and performance, under the right leadership, in spite of last-minute shuffling.
Cheers - Howie