AndrOpen Office is "the world's first port of OpenOffice for Android".
The suite has all the usual OpenOffice components: Writer (word processor), Calc (a spreadsheet), Impress (presentation graphics), Draw (a drawing tool), Math (equation editor) and Base (database).
The program can open a wide range of formats: Word (DOC/ DOCX), Excel (XLS/ XLT/ XLSX/ XLTX), PowerPoint (PPT/ POT/ PPTX/ POTX), OpenDocument (ODT/ ODS/ ODP/ ODG/ ODF), Photoshop (PSD) and many others (RTF, CSV, SVG, EMF/ WMF, TIFF and more). Your documents can then be edited and exported in a range of formats, including PDF.
The original OpenOffice was built for desktops, of course, and unsurprisingly the interface is more difficult to use on small screens.
The developers have made various tweaks to address the problem, though. Some icon sizes are larger, you can scroll with a swipe, zoom with a punch, preview some documents full screen.
Version 3.0.0 (Changelog):
It's awkward to use on small devices, but that's no surprise. AndrOpen Office is improving all the time, though, and if you can't (or don't want) to use a web-based Office tool then it's useful to have around.