I know you're being modded into oblivion and it's more likely for tone than anything else. For the most part, I haven't had much trouble using LibreOffice against newer ms .(doc|xsl|...)x documents, which is much closer to open than anything from ms-office before it. The oddities tend to be the use of fonts that aren't embedded or the use of other embedded content that will never work outside of a windows context. The simpler the document, the less trouble though.
Are you actually having significant problems in your day to day use, or was this just trolling?
All of that said, I'm actually very happy to see MS opening up .Net/CLR because there is a lot of code that runs under it, and being able to port and reuse that in a linux environment. Even in my current project creating a replacement for a .Net application in node/iojs, there's a small service I'll be using that will run with mono because re-creating the piece in question would be problematic, though that piece will enable a live data migration (encrypted data) to something that won't need the .Net code in question.
In the work I do, I still have to deal with older .xls and .doc formats. Agreed that LibreOffice and open source libraries do indeed work much better with newer MS *x documents. It's pretty far from 100% though. These semi-open formats are a hassle for me, and they're a major hurdle for any organization trying to build a business built on parsing MS Office files on an open source platform.
As far as MS opening up, I won't deny that they are moving in the right direction, but as far as I'm concerned there's still a ways to go. Get complete compatibility for Office file formats, and I'll be much more sympathetic.
Are you actually having significant problems in your day to day use, or was this just trolling?
All of that said, I'm actually very happy to see MS opening up .Net/CLR because there is a lot of code that runs under it, and being able to port and reuse that in a linux environment. Even in my current project creating a replacement for a .Net application in node/iojs, there's a small service I'll be using that will run with mono because re-creating the piece in question would be problematic, though that piece will enable a live data migration (encrypted data) to something that won't need the .Net code in question.