My experience with Smashwords is that once you're approved for Premium Distribution and you have passed EPUB your book is automtically distributed to all platforms--except Amazon. I waited for two weeks to get onto Amazon before I just put it on myself. Then it went thru just fine.
According to Mark himself, if you expect to live on SW sales you'll end up in the poorhouse pretty quickly since most of their sales are to other authors. The great thing about SW though, is that they distribute to other retailers such as Sony, apple, etc.
As for myself, I've had a bit of success with direct SW sales, fifty-three in the past years, so I can't really complain because I direct with Amazon and had also switched to B&N three months ago.