I don't know people are complaining that it doesn't sound like what they USED to sound like. The greatest bands and musicians constantly evolve their music e.g The Beatles, U2, Bowie. The not so great bands churn out the same sounding middle of the road radio happy music for their entire careers e.g Oasis, Coldplay.
Being in sweaty nightclubs and living in the "North" is not where the Arctic Monkeys are now, if they carried on writing stuff like that it wouldn't be real, spoiling their previous work. Humbug showcases a mature Arctic Monkeys, experimenting and displaying confidence and assurance in their artistic capabilities. I think people underestimate Alex Turner as songwriter and artist. Its hard to believe that at only 23 he has produced 4 distinctive, brilliant albums in 4 years. Very few artists of the last 10 years can claim to be this prolific.
Anyway back to Humbug. The moment the first few notes of My Propeller kick in you know this is going to be different., the album has certain atmosphere that is hard to describe. It sound kind of dirty and sinister. There isn't many radio friendly tracks here except maybe "Cornerstone" which is probably Alex Turner at his musical and lyrical best. Standout tracks for me are Cornerstone, My Propeller, Dangerous Animals, Crying Lightning and Dance Little Liar. These songs are easily some of the best songs musically. My one complaint for their first record was that musically it was a bit basic. In summary IS their best yet and I'm waiting to see in what direction they go next. Music is an Art and Alex Turner is an artist experimenting and evolving his way to being the greatest of this decade.