4 of 4 added detail

Harry's flying skill was complimented by Victor Krum himself (book 4), who was at that time one of the best Seekers in the world, as well as Ludo Bagman, a former professional Quidditch player, sportscaster, and the Head of the Magical Games Department (no book with me at work if anyone can help me out with edit quotes)

Another interesting point is that, most likely, professional leagues would draft star players on House Quidditch teams, as there was no Wizarding college from which professional teams could recruit good players. Krum himself was drafted while still attending Durmstrang.