C. Chen and Y. Yue study in 2000 showed that users did not perform more efficiently using visualization. This was a meta study (basically a study of studies to see if there was some meta analysis that could be applied).
Users also did not perform more accurately. Users with similar cognative ability tended to perform better on less sophisticated visualization interfaces (p=.004).
My thoughts… don’t try to cram a bunch of visual data into one view. Use simpler means and you will get better results. Many people seem to want to wow ya with their charts, but neve rseem to consider if the data represented means anything to the users or is even memorable.