The truly irreplaceable product is Excel. It is fraught with quirky bugs and limitations and odd conventions (how many people actually end up storing dates before the magic February 29 1900?), yet no alternative can hold a candle to Excel. On the other hand, there are solid alternatives to the other products in the office suite
> there are solid alternatives to the other products in the office suite Are you sure? Does it not strike you as odd that OpenOffice/LibreOffice still haven't managed to replace Word?
That it has not for everyone or as a whole doesn't strike me as odd in the slightest. There are plenty of reasons to use Word. Aside from the fact that it's solid itself, it also has a metric ton of inertia. Those using it already have the license or pirated copy, already know it, have legacy documents using it, and are generally otherwise are left with very little reason to switch to something merely because it's a "solid alternative."