The Zettai Karen Children anime is decent, but it has too much filler to actually be called good. The worst part about the filler is that it mixes itself in to all the real scenes from the manga, so that it's impossible to just watch the good parts and leave out the dross. In addition, it cuts things that were in the manga, rearranges the order of presentation, and just freely tramples over the source in every possible way. Every abomination of the spirit is done to this poor show.
The manga, on the other hand, is an epic classic. It's going to end up as one of the longest manga series ever made. It has just the right mix of comedy and drama to keep things suspenseful yet relaxing. Though every long manga series has its ups and downs, the good outweighs the bad and several delightful scenes stand out in your memory for the long term. When the ten year old esper squad 'The Children' decided to kill their own supervisor in reprisal for her reliance on corporal punishment, the show really carved a niche out for itself as a lesson on how to raise children and how not to raise children. In addition, the villains at Pandora get along with each other so well you can't help but love them, which makes for a much more interesting conflict than if they were just whacked out psychos. That the girls genuinely do become better people (and better looking too!) with age and maturity reflects well on the idea that people really can change and improve over time.
Until the manga ends in a satisfying way, it's never out of the 'danger zone' of becoming bad overall, just like Hunter x Hunter ended everything so terribly. Which, by the way, has gone on yet another indefinite hiatus. What a terrible manga. Can't they just cancel it already and be done with it? However, Zettai Karen Children is slated to end during their 'high school years' so things will probably be wrapping up soon enough. The doomsday future that had been the defining aspect of the series has already been cured, and Hyoubu Kyousuke has already been turned into a hopelessly naive good guy, so there really isn't much drama left to elongate the series over.
Just like Negima and Freezing, Zettai Karen Children is a must-read manga even though it lacks a must-watch anime. The anime butchered its worth, but the manga is perfect all on its own. Claymore's true ending is coming up in only a couple months, so be on the lookout for another series that the anime got all wrong finally done right in its original form.