You can see the direct quote on that site in the link above, but it boils down to this:
1.) When Perez took the job, he had no idea Morrison was writing Action Comics five years earlier, so Perez couldn't really write what he wanted, as he had to wait for Morrison's story to unfold, and Morrison wasn't sharing the details of his book with much of anybody, leaving Perez in a holding pattern.
2.) The final creative decisions were not in DC Editor in Chief Dan DiDio's hands and...
3.) Often times, Perez found his scripts being rewritten by higher ups - so much so that he essentially gave up on it. He would turn in a script, and tell them to change whatever they wanted and not even bother to consult him, assuming they'd change it and change it back on whims and make it all more hassle than it's worth.
4.) When Keith Giffen came on to replace him, he called Perez to make sure he wasn't being fired, and Perez told him he couldn't wait to get off of Superman. Seeing as how Giffen is also out the door already as well, it would seem to be a mutual feeling.
So the notion that DiDio was "no longer the last word" quickly leads to speculation that the folks behind Man of Steel, the fingers-crossed-hoping-it-works film franchise reboot of Superman, might be dipping their editorial fingers into the comic book pot as well - Lobdell's first issue featuring Jor-El, who has a big part in the movie personified by Russell Crowe, lends a bit of credence to that. This also supports Crave Online's Iann Robinson's continued complaints about Morrison just doing whatever he wants to do at DC without regard to others, and some critics' assertions that the New 52 stunt was not planned very well at all, as far as having a clear road map. DC couldn't even tell Perez which characters still existed after the reboot, and thus who he could still use in his stories.
Before we start thinking it was an entirely bitter experience, however, keep in mind that Perez is still working on the Second Wave New 52 book Worlds' Finest. Still, this seems to indicate that there's more volatility behind the scenes at the DC Comics offices than we may have initially thought with the whole New 52 unified front. Here's hoping Superman can get back on track soon.
