The bulk of my work is now on 15.4 inch screens at 1280x800. This is a very personal choice and I find display quality to vary quite a bit. Your eyesight and your requirements should make this decision for you and not what others use.
The reason I gifted my 17 inch laptop to my brother was simple. I found it too big to carry around. The weight was fine, just the sheer size was annoying.
I'm torn between the various resolution options available for 14-16", 5-6Lb. laptops. It seems like the new 16:9 1366x768 is becoming pretty popular, but my concern is whether I will have to do too much scrolling when reading documents and web pages. On the other end, putting 1680x1050 on a 15.4" screen seems like it might be a bit hard on the eyes, or am I wrong? Most of my work is reading PDFs and Word docs, and some use of spreadsheets and such (where I am willing to tolerate some side scrolling if necessary, since I do less of this work).