It integrates in the current DocViewer application and it can handle various office document formats (both LibreOffice ones and MS Office files) which is nice.
There are several things to do (a touch-based zooming, for example) but in general it works very well. It’s just a viewer (so no editing and – at least for now – no clipboard support) but it’s probably just enough for a phone. I have very mixed experience with editing of such documents on small touch-based devices (phones, PDA’s) so I see no problem with the fact that it is only a viewer.
All the main functionality (an ability to see files an zoom them if necessary) is here and the application feels to be stable so far.
So for the installation on your phone you need these steps:
wget http://people.canonical.com/~alan/docviewer/20151106/com.ubuntu.docviewer_2.0.193-beta_armhf.click pkcon --allow-untrusted install-local com.ubuntu.docviewer_2.0.193-beta_armhf.click sudo click register --user=phablet 'com.ubuntu.docviewer' 2.0.193-beta
After that, your phone will be able to handle ODT, ODS, DOC, DOCX, XLS and other strange file types!