This is one of the most assinine features I have ever had force-implemented by Apple. In the past few weeks I have sent no less than 5 voice messages to folks inadvertently and never even knew it because it was done by fat fingering. There were plenty more that, thankfully I caught before they inadvertently got sent. The issue is the button is right where my thumb sits naturally and usually the damage is done as I am putting it back in my pocket after sending a message (it rests on the screen long enough to activate the record function).
I will never use this feature. Forcing us to leave it turned on won't ever get me to use it. I am sure someone out there can benefit from voice text - but it isn't me and this one is almost annoying enough for me to go to a different brand.
Even the option to disable per-message thread doesn't work on my phone. I have no choice but to live with this.