I listened to Dig Down once and I still have that chorus playing in my head. That might be because either it's incredibly catchy or because it's incredibly easy and unimaginative. Also, Barcelona by Freddy Mercury & Montserrat Caballe keeps playing while thinking of Dig Down, because it has the same chords. I hope I'm not alone with that
Dig Down is indeed a Madness rip off, the opening synth alone gives that away. But Madness had a climax at the end. They could have added a nice huge chord change in the end, but it just ends with the same chords that have been played through the whole song.
Let's see if grows on me. I didn't like Madness in the beginning either. Dig Down is also a Queen rip off, just as Madness was.