I use LibreOffice, and I've never had a problem opening, writing, and sharing MS Office files with Office users. Supposedly incompatibilities exist, but in however many years of everyday use, I've never encountered a problem.
In fact, at my previous job I used LibreOffice to create the MS Office templates for standard company documents (letterhead, invoices, etc.) because it was far easier to create consistent layouts. (By contrast, Excel still employed some weird, subjective column-width calculation at the time that involved numbers of characters in the default font).
Office can now read and save to OpenOffice/LibreOffice's file formats, which means Microsoft expects that a good number of their users have to share documents with OO/LO users.
I guess it will come done to how the Word or Excel files were formatted. The simpler the better. I got my copy of Office 2013 for about $30 as the company I worked at qualified me for the big discount. I tried WordPerfect http://www.wordperfect.com/us/ but creating a Word doc with a table as an example did not open with the table in the same position or size in Word 2013.
I just downloaded LibreOffice and tried it out. I had used OpenOffice before and that is where there were problems.
I created a couple of tables and some text of different fonts and size as a Word 2003 .doc and Word 2013 .docx file and it opens in Word 2013 looking like it does in LibreOffice. I made changes in Word and saved then opened it in LibreOffice. It looked the same as in Word.
So for Word I would defiantly use LibreOffice as Word can be a pain.... The program seemed more responsive too.
Why Microsoft Word must Die
http://www.antipope.org/charlie/blog-static/2013/10/why-microsoft-word-must-die.html
I printed the docx one from both programs and they look identical so I am sold on LibreOffice. I also like the small print box that comes up in front of the page instead of Words way of completely taking you out of the screen so you lose focus.
I also like when you use the LibreOffice shortcut it shows your documents as thumbnails plus has links to all the other Office programs.
I do not use Excel much so others would have to post about the Calc Spreadsheet vs Excel version.
I see LibreOffice needs an email program. (I use Thunderbird email program)
Also check out this link for extensions and templates for LibreOffice: http://extensions.libreoffice.org