I was set to get the high res screen, but just to be sure I went to my local Apple reseller to see the difference for myself. Ofcourse they didn't have the 15" high res, but I was told that I could compare the standard res 15" to the 17" screen, since the 17" would be comparable to the 15" high res screen (15.4" 1680 x 1050 = 129PPI and 17" 1920 x 1200 = 133PPI, so text and icons on the 15" should be a little bit bigger compared to the 17").
When I got to to the store the text and icons on the 17" looked very small and I was sure to get the 15" standard res. However, after playing with the 17" for a while, the text on the 15" looked really big and less sharp and I was surprised at how much I noticed that I couldn't fit as much on the screen as I could with the 17".
What I mean to say is: I think the higer res takes some getting used to. Can anyone corroborate this from personal experience? (I'm still on the fence though about which one to choose).