I was using nVidia as well, and it was still pretty much ass.
I've always used PowerPoint for system diagrams, which happily works fine on a Mac.
I haven't had any issues with Excel going back and forth, even with conditional formatting. But yes, stuff happens with compatibility, always.
That said, I just had a chance to use Pages from Mavericks last night, and wow so compatibility very impress. Track changes and everything.