I tried PDF Expert a few months ago, bought it within the hour. It's fast, smooth, does everything I need without a hitch. Costs less than the slow, awkward and buggy PDFpen, too.
For those on a tight budget, I can recommend the free Skim for viewing, and for manipulating PDF files, PDF Genius ($14 on MAS). Not a single-application solution, not as slick looking, but it gets the job done.
Doesn't do OCR. I stick with PDFpen for the time being. But I like the GUI of PDF Expert. Also, editing text (as has been noted before in other reviews) is not as good as with PDFpen and requires a background that's cooperating.