Very early MBP's had an inverter whine which changed with the level of the backlight. This was resolved pretty quickly.
The rest of us were left with the classic whine which you're hearing. You'll probably find that when the machine's busy under load, the whine becomes quieter or intermittent.
I've got used to mine, to the point where I no longer really notice it. Within the past couple of weeks, Apple have acknowleged the problem, and current logic boards do not suffer from the whine. If you can be without your machine for a few days, AppleCare will swap out your logic board for one of the new revisions.
Personally, I can't have mine go away for a while, so I'm living with the whine. However, I have contacted AppleCare to let them know I've got the whine. I'll probably get the board replaced before I sell it on.