You'll get no flames for me. I fully support legal immigration. I think that if people want to come here, and are willing to work hard and take on the responsibilities of citizenship, we should make that possible.
What I don't support is a two-tier system, where there is the Citizen Class and a Sub-Class of Guest Workers.
You are right, just check out Germany's experience with the Turks and other moslem guest workers the last forty years. Beyond that, the fact is, we don't have to tolerate illegals to gain workers. There are an ample supply of people who want to immigrate legally but can't either because of corrupt laws or incompetent bureaucrats or both. The hypocrisy of the Bush position is clear: open the legal gates to desirable legal immigrants and you will have all the workers you want, minus almost all of the downside of illegals. There is not one single valid economic argument in favor of illegals.