hmmm, you didn't mention what mac you are buying (laptop vs. desktop), and bluetooth has more advantages for one (laptops) over the other, imho.
for a laptop, bluetooth allows you to use a bluetooth-equipped cell phone as a modem when you are away from a wifi hotspot (or don't have an airport extreme card installed to begin with) to get an internet connection. additionally, many laptop users have a specialized set-up at home for ergonomic purposes that requires setting the laptop up on a stand that would make it difficult to type on directly. so, a wireless keyboard and/or mouse are usually helpful.
for a desktop, i don't think it's as compelling an argument, but, i own a powerbook, so i could be biased here. if cords get in your way even while at a desk, a wireless keyboard and mouse would still be very useful.
regardless of whether you're getting a desktop or laptop, bluetooth does offer easier ways to sync phones and pdas with your mac. but you mentioned that you have neither, so this is pretty much moot for you.
as i understand it, you can't add bluetooth to macs internally after they're built (unless you're very mechanically inclined and adventurous, i suppose), and you'd need an external bluetooth dongle if you decide you want bluetooth later. i don't think those are too expensive, so you'd just need to evaluate the price of an external device in comparison to the BTO option price.
i can't think of any other external devices that would make it worthwhile, outside of keyboards, mice, cell phones, and pda's. one thing to think of is re-sale value. if you think you'll upgrade your mac in a few years and would therefore sell it, having bluetooth BTO could be very helpful.
i use a bluetooth keyboard and mouse, and have a bluetooth cell phone (nokia 6620) to use as a modem for my powerbook and share files between the two. i also have a bluetooth headset, which i love, for my cell phone. bluetooth is my friend!
good luck in making your choice! btw, what do you have against cell phones and pda's?
marianne