Seems that they all whine a little bit - nature of the beast. Some guys have posted that they quieted theirs down by replacing the power steering fluid with automatic transmission fluid. They're both hydraulic fluid, don't know why it would make much difference (maybe viscosity), but apparently it does.
Mine makes a little noise, but just a very little and it seems only when I'm turning the wheel while stopped (which I guess is when the pump is working the hardest) so I just ignore it. Not worth worrying about unless it was to start getting real loud.
Of course, clean fluid is important.