Is autotabbing in forms helpful or harmful?

I work in an environment that makes heavy use of mainframe systems. These systems are costly to maintain, so a decision was made years ago to replace the mainframe with web based systems.

As more people move off the mainframe to the web, a common request is that we implement autotabbing (i.e. automatically move the cursor to the next field once the current field has been filled in). I am generally opposed to autotabbing, but have no data to support my position.

Are there any quantifiable arguments for or against autotabbing? Specific research in this area would be much appreciated.