I have a MacBook, and it is my only computer. (Well, that's a lie: I have an old iMac G3 lying around, a 2004 HP laptop, and occasionally a random few-years-old desktop PC that I buy for cheap at auctions when feel like playing around...but my MacBook the only computer I normally use...except last fall when I sold my old white MacBook in anticipation of a September refresh that never happened and left me waiting, iMac G3 in hand, until late October. That was not pleasant, but it's my own fault.
)
Anyway, I don't understand why most people, if they have a MacBook, would need more. With enough RAM and HD space, it can do pretty much anything
most people want. It seems like a waste of money to me to buy it just to have it. (I do programming, personal accounting, write papers in LaTex and other grad school "homework," Web browsing, e-mail, and occasionally use OpenOffice.org, and my MacBook suits me fine.)
I also have an external display and keyboard/mouse, which gives the MacBook a more "desktop" feel. But I didn't use an external display on my old MacBook, so for a while I was using the 13.3" screen and even that was OK (but I definitely enjoy the larger screen). The only bad thing is that with my external mouse, I can't do any of the touch gestures that you can do on the touchpad...but, on the other hand, I have a few extra buttons to work with that mostly makes up for it.