Here's the key feature of Numbers vs. Excel: It not only has multiple Sheets, but multiple tables per sheet. Besides tables you can for example add text fields and images to a sheet. This makes it much much more natural to create reports and it encourages to split up your huge tables in logical units.

Oh and one other thing: Modifying columns/rows is consistant over all iWorks applications: Alt + arrow-keys let's you insert rows/columns above, below, to the right or left. MS Office's inconsistency and lack of hotkeys for such an essential feature makes me rage every time I use it.

Numbers sure has shortcomings though: no pivot tables, very limited scripting support, limited filtering / data manipulation. That's why I look at it as a very good spreadsheet tool, but not a data analysis tool - that's when Excel and/or Matlab come into play.