Good Gear Guide
In Pictures: The must-have iPad office apps, round...
The rest of the iPad spreadsheet editors
DataViz's $16.99 Documents to Go Premium offers the basics, but no more. It's languished for several years, so it's not a good investment choice (the recent update was trivial). It does not support printing or PDF export.
Picsel's $9.99 Smart Office 2 is simply unusable due to a very poor user interface and limited capabilities.
In Pictures: The must-have iPad office apps, round 7