Planet13 - 2:25 pm on Jun 27, 2011 (gmt 0)
But in any case - LET YOUR USERS DECIDE. :-)
Test this out, but I am not sure I would agree with rocknbil on this.
I would prefer, if at all possible, to do A/B testing with a set number of images per page, and then see which format performs better.
I tend to think it has LESS to do with the amount of scrolling one has to do and MORE to do with the amount of choices a visitor has to make when on a screen. Also, I would be sure to put the best performing / best ROI products at the top of the category page.