I don't think its an irational fear, maybe because I've been there.
I start out with speedscript then geoworks on a commodore 64 then on to somehting on an amiga then wordperfect on a pc then ms word, etc. I've had to export/import documents many times and always lost somehting in the translation that I had to recreate.
I've also used apps like MS money 97 and bought the next version (Money 98) and found it wouldn't import my money97 file and a paid support call to Ms tech support left me with "your file is corrupt, start a new one" so I was stuck running the 97 and 98 versions on two differnet pc's if I wanted accessto my old and new data.
I've made it a standard that my files and software have to be open now and I'm finding that I don't really miss anything, the features of propritary software are somehting I find I don't use often enough to remember how to use them and in the time it takes to figure those features out I could just make something work in an open package.