Libre Office incorporates many major improvements which had been originally introduced by a splinter group called Go-OO, of developers who had become frustrated with the sluggish response of Sun Microsystems (now Oracle) to new code offered to the project. Those changes included better importing of MS office files and many user interface improvements.

Libre Office has also had lots of dead code and general internal mess cleared up, and is a far fitter product than Open Office. It's not surprising that the major Linux distributions are moving to Libre Office, and many developers have joined in now they can actually get something done.

Go to libreoffice.org and try it. It's free and it works well. I've been using it (and OO before) for years.

The main problem with OO or LibreOffice for a few users is where a big investment has been made in development of Excel macros that don't easily port to LibreOffice. Rewriting that code could take some time.

For everybody else it's a fairly easy switch, apart from having to learn to do some things in a different way. But the longer you use it the more you appreciate that each and every upgrade to the latest version is as free as the first download, and all your old files are compatible with the new versions.