Look at the arrow on this page — it indicates that there’s a horizontal scroll, and there are more products available by scrolling to the right. I never thought I’d see this again, and certainly not dell.com.
And it’s a bad design. Not just because Jakob Nielsen says so, but because I had to look through this page four times before I noticed that I could scroll to the right. I knew the computer I wanted to look at was on the page somewhere, but I kept scrolling down and not finding it.
You just don’t expect a horizontal scroll and the little sentence of gray text is not nearly enough to overcome that. (And maybe that’s the point, since the cheaper stuff is to the right…)
All the argument in the world about the practicality of a horizontal scroll will never get around the fact that it’s just goofy and not the de facto standard.