This is my nickname (full name being Mason) and I absolutely adore it! I think it's very cute, with a floral feel to it due to its similar spelling to daisy. An adorable nickname for a kid, maybe less so for an adult, but my family still uses it for me in my 20's.
Cute, but I prefer Maisie because it looks better written down. I always used to think Maisie was a variant of Maisy, not the other way round. Funny that.