Every guest worker plan I've seen introduced includes some sort of amnesty for criminal invaders.
This difference between the various guest worker plans is what the pubs and the dems are dueling about in Congress.
In contrast, if a law is changed so that what was illegal is no longer unlawful, then by definition, that is not amnesty.
For example, it used to be illegal for slaves to runaway. Many abolitionists refused to obey the law and harbored the runaway slaves. Then the law was changed so that there was no slavery. The runaway slaves were no longer in violation of the law even though they had broken the law. The abolitionists who had broken the law by harboring runaway slaves were no longer in violation even though they had broken the law. That was not amnesty. That was a change in law.
What Bush and other immigration sympathizers propose is by definition not amnesty. It is a change in the law that would make, be definition, illegals legal.
One inherent illogical and unsupportable argument of some (but not all) immigration critics is the whole thing about "illegal". A law can be passed to make it legal and voila, the illegal argument evaporates. That leaves those immigration critics stammering in embarrassment and rage because they had a bogus foundation for their argument.
Some (but not all) of those immigration critics who base their argument on "illegal" don't want to admit it. But they are really anti-Hispanic. I've worked in offices where there are illegal Indian immigrant IT workers and illegal Mexican cleaning crew. There is always more antagonism to the cleaning crew than to the IT workers. The terrorists came accross the Canadian border. Fact. My Canadian (non-terrorist) relatives illegally cross into the US all the time without even thinking about it. But the Minutemen are on the Mexican border.
There definitely are some immigration problems. Bush is not properly addressing some of those problems. But the current anti-immigrant rhetoric is dominated, not by the legitimate issues, but by illogic and non-facts that lose the immigration critics credibility.