I agree with Steve here.
Being an old PalmOS-User I'm sort of used to this kind of feeling:
Riding an old but trusted and still very reliable horse till the end may come one day ...
So we will stick to what we have (there is no epub-reader for the "dead" Palm OS and never will be) and read mobipocket and .prc from websites with copyright-free or cc-content or independent Publishers / Authors as long as it is possible.
But if this could help to cut the number of formats in the long run then there could be something good in it.