From Fred Barnes:

...Consider how the proposed plan would be seen by a poor but ambitious young man in Mexico. He knows that getting in line for legal immigration would probably never get him to America and that staying in the United States on an illegal basis has its drawbacks. But now there's a legal alternative: Get across the border, find a job (a menial, entry level job will do), and sign up for a 3-year work permit that's renewable. This is quite an incentive. If the Bush plan passes, word will spread fast that now's the time to get to the United States any way you can.

AGAIN, let's applaud the thinking that underpins the Bush plan. And let's praise illegal immigrants for their moxie in getting here and making America a better country. But let's not have any illusions about the practical impact of the plan, which is that more will come and few will leave.