In practical terms, cross-platform is merely an illusion

As the video here shows, owing to regulation, Microsoft needed to give Apple a cushion and a lifeline in return for some favours (Novell's deal was eerily similar). It was a self-serving deal where Microsoft committed itself to offering Apple some Microsoft Office scraps. Never mind those Windows-only functionalities.

“It was a self-serving deal where Microsoft committed itself to offering Apple some Microsoft Office scraps.”This old development had some victims (dead companies) and the PC/Windows version of Microsoft Office was never comparable/compatible with the Mac version. We pointed this out before (with examples), if only just to show that even Microsoft is unable to make OOXML work. It's failing to port the very same piece of software to another platform without OOXML coughing out errors.

Microsoft Office for Mac has other issues, such as bugs and lack of integration, according to this very recent CNET Asia blog:

For me, the Mac version of the Office is like another new application. It lacks the functionalities of the PC version, especially with the address book in Entourage. The interface is horrible and I just found out today that all the personal pictures I tagged to each of my contact don't sync over to the Mac (strange, it works for the iPhone). The other weird thing was how Entourage messed up all my appointments. All my appointments synced over to the Mac were set to a timezone 8 hours earlier than the local time here, resulting in 1,302 duplicate appointments on my Exchange server account.... and that syncs back to my PC, my iPhone and practically every gear I own that syncs with my Exchange account.

Does anyone still believe that a complete implementation of Microsoft OOXML (not the same as ECMA OOXML) can work outside Microsoft Windows and Microsoft Office combined? In practice, only Windows users can properly exchange documents encoded as OOXML.

While IBM is no angel (still refusing or failing to address concerns about software patents), at least it supports ODF, which works uniformly across different platforms. To IBM, there's hardly a conflict of interests at a platform level. User "Mchvany" seems to have just uploaded a bunch of Lotus commercials, but it's proprietary software and therefore its use is not encouraged. ⬆