Yea, if it is a major production you are better off using a pc to make MS office document. A major part of the problem is that a significant portion of the screen has to be taken up with the VKB. So only minor editing makes sense in general. I just happen to realize that if you measure the diagonal made by the bottom corner of n900 keyboard to upper opposite corner of screen you have about 4.5 inches. This is about the size of the latest high end phones screen (albeit with an different form factor). The effective 4.5 inch screen you get (compared to a phone with no HWKB) makes editing a document more bearable and probably sets a lower limit for how small a screen should be to have reasonable productivity (at least for me). The Galaxy Note has a 5.3 inch screen. It comes with an editor called Polaris. I don't know much about that editor. I'm supposed to get mine Thursday.

Another option (and my favorite!) is if Latex could work on N9. That would be great as the entire document is made by editing a tex document that, after it is processed, can be viewed as a pdf.