Hmm. That's a great question and the first time that I have ever seen anyone ask that.
My daughter got her first MBP several months ago with the idea that I would install W-7 as well. Now she says "Forget it for now, I'm fine". I am glad because it forced her to learn her way around OSX. It's not tough, but it would have been easier for her just to get confused and instead of learning, just jump out to W7.
I have used a Mac for about 4 years now, and did not install any windows OS for the first two years, because of budget constraints and because I was so interested in operating in OSX. If I would have had a windows disc when I started on mac, I still probably would have waited while I acclimated (I mean I already knew what windows was all about). It would have been too easy for me back then, to simply jump out of the Mac when I ran into a hurdle and would have never let OSX become second nature.
Frankly, the only reason why I put windows in was to run a windows based multi-tracker that I sometimes use in my studio. I still only use windows for that and some games and the better TV media software in WMC (no flame war please). I
i feel confident that you will be amazed at how much you will like OSX for most of your needs instead of windows.
So my advice, run your mac and enjoy it, and then when you say "I will never return back to a PC", that will tell you that you have a handle on OSX and then you can add your windows for whatever purpose (and W7 is just so much better than XP or Vista, and Apple hardware runs windows so much better than a pc).
Hope that all makes sense.
And when you decide to install, there are many good threads here that can assist you if you run into a problem (it's pretty straightforward though).
Keep us updated, and welcome to Mac.