I like to commend myself as a full-on alternating player but I simply can't undermine the use of single-tap when it's best needed. Most songs play on a 4/4 beat and with that stated, alternating fits well not only on developing a basic motion that founds streaming, but also to develop a musical sense in your tapping especially since they correlate well on downbeats.
Truth be told that you can't unlearn single-tap. That is a law written in you when you first start playing osu!. So by adjusting to alternation you expose yourself to the goods of both single-tap and alternating.
I can't say that I've used single-tap to its maximum potential but I find it as an easy get-out-of-jail-free card with its universal 1/1 musical denotation to a sudden rush of unfamiliar rhythms that would normally confuse my alternating motion to choke.
Alternating is easy for the most part, but the real trick to practicing it is being able to apply it in creative bursts of notes and sliders. It's not rocket science to Z on the first 1/2 beat, X on the next, and rinse and repeat. But for say... tap Z, hold X, tap Z, tap X, hold Z, tap X (imagine a dense string of sliders and notes) it takes real practice of alternating to work out right.