Here goes:

I really like Ubercart, but in order to make it a viable option for my bookstore's site, I have to be able to import and export any data inside custom product classes CCK fields. For example, the "book" class has fields for subtitle, authors, pages, format, and so on. Ideally, the module would be able to import/export data to/from .xls spreadsheets, .csv, and tab delimited at the very least. If you can make it handle excel-generated XML, so much the better

As the store has over 10,000 items, and adds about 100 new items a week, the module should be sturdy. Ease of use is also important, as the intended end-user is your average $12/hr wage slave.

Hope that made sense! Look forward to hearing from you