What I have noticed with regards to successful advertising on facebook is that small businesses have success by treating facebook the same way they would treat real world social interactions. Meet new people, get to know them a little and say "by the way, this is my business, you should come by". People are more willing to do business with someone they have a connection to. It's a great tool for the mom and pop businesses.
As a facebook user I don't find myself clicking the ads unless there is content, such as a movie preview or something of that nature. The branding itself does burn into my mind quite often though.
As far as my own marketing goes, I run a few facebook pages, I haven't had a lot of measurable success with those other than a little bit of interaction with my audience. I do use a like button for each page of my website content. I might only get a handful of likes each day but the way I see it, the more my content is shared, the more people will be inclined to link my content. I had marginal success by posting a sale I was running to my personal fb account but the amount of work I put into it wasn't worth the benefits.
My view of facebook marketing right now is that it's best to treat the social network as a social interaction in the real world and it is good for branding in general. As far as direct sales though I haven't seen much to get excited over yet.