Yes it it is.
But you probably want the long answer?
After my interest in open source programs started in late 2010 I decided to try Open Office to see if could use it instead of MS Office I use at work. So for over a year I have been using LibreOffice (used Open Office for about 3 months and then switched to Libre to try it out) instead of MS office and at work I use word and spreadsheet programs allot. Every time I found out some feature MS Office has I tried to find the same in Libre Office (and always found the same function in Libre) and basically used it as my main office application. During this time there has been one word document that didn’t open correctly. The formatting had changed a bit but the document had tables and stuff but the document had all text and nothing was missing. Excel is pretty import for my work as well but of all the Excel documents I have received, created myself, e-mailed to others who use MS Office, I have in total had two documents that had errors or needed to fix something. One document didn’t’ calculate correctly between sheets and the second was using allot of macro work and Libre showed some errors and froze when macro was enabled.
I personally do not like the banner MS Office uses, I probably would get used to it but I just felt I was always looking for the tools I needed so I was very glad after installing Libre Office (and Open Office) to see the “old” look and having everything at hand so to speak. The learning curve isn’t so steep with Libre Office, plenty of YouTube video’s demonstrating how to do things and a quick search on the web gave me all the assistant I needed.
So as far as I am concerned I can say that Libre Office can be used as a replacement for MS office. It isn’t perfect but if everybody started using it there wouldn’t be any problems and the very little problems I had have no effect on my work (except the heavy macro excel document which wasn’t in regards to my work). Future releases of Libre Office will constantly improve the program so I don’t think I will ever need anything else than Libre Office.
For those who use MS office at work and recive many open office documents from other there is a simple solution to the compatibility issue of MS office. Just download Libre Office.