Not as horrible as they say
Good: The story is pretty good. The cut-scenes have great graphics. The amount of guest star characters is terrific (though many non-comic fans probably won't know one or two). The amount of gadgets that Batman has is great.
Neutral: Combat is somewhat limited. Little to no combos. Using handcuffs during battle can be very annoying (because while handcuffing one enemy, another starts kicking you and the enemy you were handcuffing gets up)
Bad: Camera angles are extremely annoying. You could be running straight and then the angle will change and you'll turn around. Certain areas are too dark (especially on certain levels that involve walking on roofs, in which you can just walk off the building to your death)
So yes, it has a few faults. But it isn't a horrible game. Is it good… yeah, I think it's pretty good. At least not as horrible as most think.