Well, I really like it, and I imagine a young girl with dark hair.
This is the poem I associate with it:
http://www.tetrameter.com/hopkins.htm(it's actually called Spring and Fall)
Maggie spoils it I think. Where Margaret is understated, solemn, and timeless, Maggie is harsh, childish, and modern. I prefer it without a nickname, but my favorite nickname for it is Mar. Meg is kind of cute. I think Daisy as a NN for it is silly.