As someone who uses the free version on a regular basis as a complement to my installed copy, it gets the job done...98% of the time. Once in a blue moon, there's some weird formatting issues but it still renders most Word, Powerpoint and Excel documents like a charm. It also auto-saves everything to a OneDrive account and has a Time Machine style backup system in place.
Honestly, you get me started on the Office/OneDrive combination and I won't be able to stop talking about how it is a great example of how to do a cloud based solution right (to be fair, if you're an iWork user, iCloud/iWork probably gives it a run for its money).