Of the MS apps, Excel is quite useful.
Word is however very limited (unless you have a subscription): no track changes, you cannot insert page break, etc.
In Powerpoint I have no idea how to edit.
I tried OfficeSuite which has most of the functionality I need, and you can actually buy it (not just rent it). However, the app is very sneaky, and you need the font package to use it at the end (without fonts nothing can be formatted... no printing... etc), so double the price in Google play.