@evildictaitor: I would much rather have support for more file formats. I still get the odd doc or xls from people. The other day I got a wps file!
Like you say, I could demand the ability to open WordPerfect, Quattro, Lotus Notes, and reverse binary encoded paradox indices, but that's not the right way of going about it. I don't think that the WP team should spend time supporting every file format under the sun. Instead, this sounds like something that Hotmail/SkyDrive needs to handle. Give me a message that says, "We can't open this document locally, would you like to download a converted version?" Instead of spending the time on supporting stuff that nobody on the phone cares about, you can use some of the conversion expertise that they already have, leverage the cloud, and still provide some advanced features without compromising the security or performance of the device. You also get the ability to support the desktop, iOS, Android, etc with a single backend service. You go from spending a lot of time on a useless feature that a ridiculously small number of people will care about, to something that's much more useful.