I guess one way to look at this thread is to imagine a continuum:
<Downhill mountain biking ---------------- general commuting ------------------- long distance road riding>
A CX bike cover a broad stretch of the middle ground well, better than a hybrid, for example. But if most of your riding is at both extremes, you'll probably be disappointed, and much prefer to have two bikes. The same could be said with another continuum for touring: if you either commute or do 2 month tours, you would probably prefer "the ultimate touring bike".
I think I'm lucky that so much of my riding is still in the sweet spot - commuting, short tours, mostly non-technical singletrack with non hardcore mtb'ers, shortish road rides, no racing....
Steve