My DD is a one and only. She is lovely, polite, generous, not remotely spoilt. I know I am biased- but this is what her teachers & other mums have said, and I get a lot of congratulations about her.
She does need me to be her playmate and that is tiring, but her best friend is one of 3 and also insists on her mum being her playmate. They are equally good at self directed play.
I find her interesting, she is very sensible (another thing that is commented on even by strangers overhearing our conversations on the train!) And I don't want a second child changing the bond we have in any way, because through each developmental stage I enjoy how we relate to each other, as individuals. She is funny, clever and confident without being pushy.
I'm sure things will change when she hits the teenage years and turns into a sulky, mardy thing as she does already get a bit of sass when I tell her to do things she doesn't want to, but at the moment shapes up that attitude when I do my 'mum face'! And when she is a teenager - I'll only have the one to deal with!
I'm looking forward to her being an adult, so I can hear all about the life she makes for herself.
I love having one child, and I hated being pregnant, so things are working out here.