They seem to have fixed that, at least for me all the top results are Pinboard clients or other products with Pinboard in the name.

With the ads it really feels like Apple is playing all sides, they almost always show the competitor first. When you search the competitor it's a different competitor at the top. You can keep going until you terminate at some app that presumably pays top dollar to appear as an ad for themselves right above their app in the search results. The only thing I'm surprised by is that they even allow people to put ads over their own first party apps