I found this page when trying to figure out how to get LaTeX to use Helvetica. Proved quite useful and insightful.
One of the most interesting bits was this note:
The dirty little secret here is that when you do this, you might not be getting the true Helvetica but rather it's very close cousin Nimbus Sans. That might depend on your system, and LaTex setup though. Nevertheless, Nimbus is still far better font type than Arial.
My question is can you tell the difference and does it really matter whether or not you get the true Helvetica, or a close-enough knock off?