I concur with the rest of the commentors. I was looking into whether I could use iPad as my "road computer" and was most of the way to getting there. I can deal with working in Pages and importing/exporting from/to Word but I rarely work a document other than in track changes. The combination of not being able to do this and the fact that Pages simply accepts all changes in the imported document is a deal killer.
It's a shame. In a lot of ways, the iPad would be a big improvement on my laptop. It is obviously not a substitute for my iPhone so, if it is not a substitute for my laptop either, it is just one more piece of gear to schlep.
If Apple wants to sell this thing to lawyers (yep, I'm one too)or other people who really work documents they need to solve this problem. Best would be to allow Word but track changes, in one format or another, is a requirement for serious document processing. I can live without the ability to put a giraffe anywhere in my document I want to but track changes is serious.