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.
Green Lantern. Under Geoff Johns, Hal Jordan and the Green Lantern Corps have become the center of the DCU. Yes, bigger than Superman, Batman, and Wonder Woman is the Green Lantern. At least for a while.
Superboy Prime, to the point where he is considered unreadable when someone else writes him. Case and point: Countdown to Final Crisis
The Flash had most of his villains redone, starting with a strongly anti-hero Captain Cold, spinning through most of the Rogues' Gallery. Everyone was adjusted and made deeper, with their personal storylines continuing. Perhaps the most drastic change was the death of the first Captain Boomerang and the rise of his son to take his place.
And Parallax. In fact is it safe to admit that he has pretty much made Green Lantern the most consistently good comic of the last 5 years?
In one issue, Johns took the Tattooed Man from a joke to an anti-hero powerful enough to earn his own mini-series. (Admittedly, it took giving someone else the name and powers to do it, but the new Tattooed Man is still awesome.)