Only One Category

Mostly, primarily, I highly value being able to assign a post etc to more than one category. Many things naturally 'belong' in different categories ... and there is even a game or trip, in which one deliberates crafts content to straddle different worlds/levels (photo-composition is wonderful for this).

However, I would also very much like to have an 'unimpaired' hierarchical categorized URL (aka 'permalink'). It is much easier & better that each post have a "unique" category, if the category-hierarchy is going to build the link ('breadcrumb'-fashion).

If WordPress officially decided to offer the option of a 'clean' category-permalink (without the 'empty' or placeholder hierarchy-level), I would then be 'hard up against it'. 'Uh-oh ... decisions, decisions.' But as it stands, the official option is unattractive, and easy to decline.

Ideally, we might have a Primary category for each post, and then any number of Secondary category assignments as well. In any situation where a post should have "a" or "the" category, the primary assignment would be used, and the others ignored. But we're not holding our breath for anything along these lines.

Those who do like to use multiple categories, but would also like to have category-URLs (the 2 do seem to run together...), could shift to unique categories and then partially compensate by making heavier use of Tags. And tags can also benefit from enhancements, theoretically from WP HQ, and pragmatically through various plugins. Tags are a less 'touchy' entity than categories, and better-suited to 3rd-party modifications. We can 'play' more with tags, without sticking our neck out as much as with categories.

But no - I'm not going to do Only One Category at this time.