David Hayward has blogged at Public Address on why the NZ Bill of Rights should be entrenched as supreme law.
The major problem I have traditionally had with doing this, is that it will elevate the Supreme Court to the final arbiters of law, and by doing so it is inevitable tha appointment of such Judges will become far far more political with more weight given to their political views than their legal ability. We see this in the United States. Do we want confirmation hearings for judges?
However I greatly value my rights, especially my right to free speech. And the Muhammed cartoon controversy made it very clear that when push comes to shove most politicans will not protect my rights to free speech against other pressures. Instead they pressured the media greatly to self-censor.
That one episode has been enough to move from from mildly against to mildly in favour of an entrenched bill of rights.
However as a safeguard I do quite like what Canada has done which is to have a notwithstanding clause. Basically it allows Parliament in special cases to over-ride a judicial striking down of a law for up to five years.