These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Base Breaker: Mylo Xyloto. So far, fans have either fallen in love with the new, poppier direction or lambasted Coldplay for "going mainstream." (Whether or not this will change when the album is actually released remains to be seen.)
Viva la Vida before this, to a small extent. While most loved it, there was a sizeable minority who detested the "pretentious" direction and wanted a return to the old simple, poppy style. Oddly, these don't like Mylo Xyloto.
Magnum Opus: Either A Rush of Blood to the Head or Viva La Vida.
Rescued from the Scrappy Heap: Many critics and general music fans only started to like the band after Viva la Vida or Death and All His Friends, and in particular the release of the single "Violet Hill".
Sampled Up: The riff in "Talk" (you know the one) is adapted (with permission) from the riff of "Computer Love" by electronic band Kraftwerk.
Chris Martin has admitted that "Fix You" was inspired by the Elbow song "Grace Under Pressure".
Sophomore Slump: Averted with A Rush of Blood to the Head... but somewhat played straight with the sucessor to that, X&Y.