I still think that all things being equal (and they rarely are) that re-written urls will perform better. And major retailers like big-box stores don't primarily rely on search engines anyway, as everyone knows who they are.

I do not see a wide-spread movement across the web AWAY from re-written urls, on the theory that dynamic urls consistently out perform re-written urls. It's really only here at zencart you see statements like that. Since zencart does not come with url re-writing, and re-writting plugins are susceptible to being broken by some plugin or zencart upgrade (CEON excepted, of course), the feeling is that since dynamic urls work good enough, stay with them.

Hey, I'm giving a plug for CEON here!