Is Miranda warning good or bad?

The Miranda Warning is good. It's a legal warning given by Police to suspects that are going to be questioned informing them of their rights to:

• Remain silent;
• Terminate questioning at any time;
• Have an attorney before and during all questioning; and
• If they cannot afford an attorney, the courts will provide a free attorney for the duration of your trial (meaning if you're convicted or acquitted, the attorney no longer represents you)

and that anything they say after the point of a Miranda warning can (and generally will) be used against them in a court of law.