No, but it is in the areas that matter to most people. The thing is, people (at least the people I know) don't spend a lot of time working on older documents. They are working on new documents. And when they upgrade their Office version, usually everybody is upgrading their Office version, so Office 2003 vs. Office 2013 incompatibilities don't matter to very many people. But there is no LibreOffice version that will import a complex Word document of any version without some major flaws (minor flaws are usually ok). Floating figures that move around or disappear, captions that disappear, tables that get mangled, line art that doesn't render or renders incorrectly.... If you are writing a simple office memo, LibreOffice works perfectly fine, but many people use it to do complex formatting, and for those people the incompatibilities are a big problem.