I think the surprise regarding Iceland is a little overstated. I mean, they are ranked 34th in the world and midway through last year they were around 25th. They also came close to qualifying for the 2014 World Cup and beat Holland twice in the Euro qualifiers. In their games so far they have definitely looked like a solid side and I think they outplayed England. I reckon reaching the QFs isnt really an over achievement, reaching any further would be though because I dont think they are close to Italy, Germany, France or Belgium.
A good achievement nonetheless for a country with 350,000 people and a co-head coach who moonlights as the town dentist (versus Roy Hodgson and his $4.5 million salary).