When should we use calculators in a classroom?

After I talked about my TI-89 in class last week a few questions were brought up that really made me start to think about my future classroom. How often should calculators be used? And, is it important for kids to know how to do things by hand? As we have been told a million times, technology is the future. A good point was brought up that when kids get out into the real world their bosses aren't going to tell them not to use a calculator. Employers aren't going to make sure you can do it by hand as long as you can get the job done. This is exactly why I think calculators should be an important part of any math class. TI-89's are very complicated but have so much to offer. Most of the stuff that I have learned how to do on mine has been by trail and error or just playing around. If kids were taught easy ways to compute hard problems then maybe math wouldn't be so frustrating or confusing. Don't get me wrong, I think it is incredibly important to understand the process of what you are doing, but I also think that math doesn't have to be made out to be as complicated as it is... especially if we have the tools to make it easier.