Good question. I suppose the answer would be 'define happy' :p
Seriously though, there are some songs I'm quite pleased with, and others which - particularly as time passes - become hollow to me, and all I can see/ feel in them is how/ why/ where they don't work. Other songs I carry on liking for many years after writing, in spite of their imperfections.
So, in some ways, yes, I've got a few songs in my bag that I quite like, but I can still see much room for improvement and development. But isn't that the same for most people? I almost fear reaching a point where I feel I have songwriting 'nailed' because complacency is the enemy of progress and a critical aspect of the creative process: asking 'will it work better if I try it this way?'
I'd be interested to see how the answers to this thread would change if the question was 'are you unhappy with your songwriting'?