The main reason I got upsold to the 17" MBP in 2009 was that I couldn't bear spending a lot of money on the 15.4" with its adequate but thoroughly mediocre 1440x900 resolution. Its rightful resolution is clearly the now available 1680x1050 when you compare the pixel density with the 17".
Would you take the 15 HD now vs. the 17? There is a very small price delta, and the screen is definitely bigger and is even marginally higher dpi still, on the 17. The 17 is slim, if big, and has an ExpressCard slot (which is possibly a 64GB SSD if nothing else).
The fact that the decent-res is a paid option rather than stock is a bit galling so I'm not sure. I will say that I'm very happy with my 2009 17" and will keep it for a long time.
