New Pork City is one of the worst, if not the worst, stages in all of Smash history. As said in a previous post, it can only be rivaled by Icicle Mountain.
There are many things wrong with this stage. It's just one big cluster of obscenely annoying ledges/footholds. It is very difficult to tell what is background and what is stage. Given its idiotically incredible size and unconventional 'ceilings', it is very hard to score a KO. In fact, at one point in the match, the opponent will begin to turn the tide and use it against you.
Ultimate Chimera -- Easily the most hated obstacle EVER. Though one can easily avoid it, cunning players will trick and throw you into its path. Then...
CHOMP!
It is a rarity to survive. It is immediate InstaKill.
Campers absolutely dominate this stage. I remember facing an Olimar once and the entire match consisted of him spamming Pikmin Chain while cowering in an alcove. Needless to say, it was really difficult to approach and any other attempt to close in would be easily seen.
Some players, namely Sonic, are notorious on this stage. It is very difficult to get past their wall of combos AND trying as hard as one can to not be smothered by the very stage itself.
That's another problem. The footholds. I often get tricked into trying to recover onto a wayward platform or end up hugging its bottom and end up free-falling to my imminent doom.
Most matches will take up only a specific landmass, most famous being the very bottom of New Pork City. To this end, most players will take advantage of the structural make-up. The left-most cluster of platform is where campers thrive. The bottom is where the heavy-hitters dwell and I'd assume the right-most is where vertical attackers, like Ivysaur, prosper.
All in all, New Pork City is a place of condemnation, where one will find himself thrown about the stage like a ragdoll. This is one stage that is DEFINITELY not enjoyable. At least for some...