I just started using the MS Word app on my Chromebook. Up to now I have used Google drive and a couple of other apps. I started using the MS Word app because it is the only one that I can use on the WIFI network at work. The school district I work for blocks all Google sites (must be because they have a contract with Microsoft for much of their IT).
So far I like what the app can do. First, it's free, which is great. Second, it is a web application, so you need access to the internet and it doesn't work offline like Google Drive does. Since I have a robust WIFI network at home and a decent one at work, I have no issues with being online (other than not having Google access from work). I also have a hotspot on my iPhone, so I am never without some kind of access to the internet. Third, it is a full functioning word processor, but it does not have all the functions found in a full version of MS Word. That does not bother me as well since I do not use all the functions anyway.
Finally, the app works well. I like all I can do with it. I also like how it saves my documents to the cloud automatically. I can also access my documents from several of my other systems and edit or add to them. Having this app on my Chromebook makes it highly functional. One of the biggest drawbacks to using a Chromebook is not having access to many of the standard software packages (Like Office and the like). This app is a fully functioning version of MS Word, so that is one software package that is not an issue in using a Chromebook.
So, can you use MS Word on a Chromebook? You sure can and it's free!