Three things:
1. Mellel’s next release will build on XML format, which means this will solve all your problems as the code will be easily readable. For small documents whose format is unimportant I tend to keep them in .rtf, and near the end of the writing stage, style it up.

2. You can always use and compose in AbiWord and than go to Mellel for styling it up.

3. On Macs there is one last solution that is really nice, when I am done with a document, that is moving it to the printing stage, so I want to preserve how it looks across all computers you can select print, and rather than print save it as a .pdf. Pdf’s are large which is not the most convient but their layout is kept in tact. (This can be done on a PC it is just harder.)

Finally if Word works for you, keep using it.  I however was really frustrated by how it worked, and what it did and wouldn’t let me do, and I think most people feel the same especially when they try out another format.  But if you do stick with Word do the world a favor and always send docs as a .rtf. (And get your students to do it.)

Having said that, I entirely agree with your ideological side. We should be speaking and writing in a format that is as widely accessible as is possible. But RTF is just not powerful enough for this. ODF, on the other hand, is. And had Mellel or Nisus had the foresight to switch to ODF, the word processing landscape would be quite different. But they didn’t. And it’s the reason I can’t use their programs.

From my perspective, I don’t see a viable alternative to word:
NeoOffice is still in Alpha, to say nothing of being horrifically slow
Openoffice is not much of a Mac application
Abiword has so many font rendering problems on the Mac as to make it unusable
Mellel and Nisus use formats that are far less universal and far less sharable than MSWord.

I’m still open (indeed eager) to being convinced that there is a viable alternative. So if I have missed something, please do make suggestions.