[rkagerer]

Once you get the basics out of the way (e.g. clean interface) I personally find one of the biggest usability impacts comes from the fact the system know their products, and lets you filter by various properties (dimensions, material, etc) which are detailed and appropriate for the category.

I wish Amazon did the same and offered more useful and accurate filtering. +/- operators would also be great (I know you can google site:amazon.ca +headset -bluetooth but it doesn't always work well).