15" is too small to be used on the lap for 8 hours a day.
Where do you get the idea the 17" is too big, when you owned a 17" notebook was it an Apple or one of the Windows units? You have owned a 17" Apple Macbook Pro. Used one for an extensive amount of time, haven't you, or are you just expressing an opinion of others as the opinion of yourself?
If Apple made a laptop the same size as say a Hewlett Packard 17" Pavillion, it would have a 20" screen.
PHYSICAL SIZE: Apple 17" Macbook Pro = Any Other Brand 15"
When I bought my 17" MBP I wanted a nice carrying case. Not finding a 17" case I liked I found the 17" MBP actually fit extremely well in a 15" notebook case. Even fits in the 15" Notebook Pocket of my Camera Backpack.
One of the biggest drawback to the 17" MBP is the price, but many will use size as reason they do not own one.
Low End 15" $1799
Low End 17" $2499
$700 is a lot of money one could use in other ways. But as one who uses a notebook as his primary computer on his lap, and on his desk I can tell you $700 is a small premium to pay for what the 17" brings you.
NOTE: Initially I bought a 15" ( $2199 ) but returned it after realizing I made a mistake and bought the 17" ( $2799 ).
i have owned more than one 17 mbp. i have been thinking about getting another one. i was in best buy with a co-worker and he mentioned wow the 17 looks too big and akward.