I agree with the OP.
I don't have a Mac, I'm on a 15" PC laptop and I think the size is perfect. 13" is too small and 17" is too big. I'm eyeing a Mac terribly but it HAS to be a 15 incher. I can't do 13".
I wish they didn't practically kill the regular Macbook line and released a 15" Macbook at, say, $1349 or something like that. Instead they lowered the price on the 15" Pros but went the wrong way, JMHO.
Of course, this is coming from the perspective of a college student so every dollar spent is precious.