A good question. I tried the Open Office app for a while. It's good, but it does require a little bit of learning. It is a single app which has all three functions, of Office. And as was said, although it can open and save as Microsoft files, there may be some differences. Keep in mind that is true only for Microsoft files and if you are mostly working with files that no one else gets, then no problems. The same applies with Apple's Pages and Numbers. I liked the Apple programs a bit more, but they are not nearly as feature rich as Microsoft's. Either one will serve you well.
Incidentally, the new Microsoft apps are significantly different than what you have. And being tied to the web, it is now much slower to open.
What I finally decided to do was to let my subscription to the web based version of Microsoft Office expire. Then I went ahead and purchased a one time download. (After removing all of the old apps, just to keep everything straight.) I don't need all those updates with new features I won't likely use anyhow. It's sold on the Microsoft site, but you have to look for it. It's the "Students and Family" version. You may be able to purchase it elsewhere for less, but when I tried buying via Costco's site, it didn't work to get the download. Something to keep in mind.
Lastly, there is a FREE version of the apps available on the Microsoft web, but you can not save files to your disk and it has fewer features.
In summary, changing over to another program is viable, but you will have to get used to some differences. I Hope this information is helpful.