Back in the Knoppix days it was first a novelty, and then a blessing that you had to boot from a CD-ROM, because it led to one amazing outcome:
Less tinkering.
Or rather - it split use from tinkering.
Systems today are designed around the principles of deferral and volatility. You can add or change anything at any time. The user has absolute freedom to tinker, but also the vendor of always-connected products has endless possibilities to update. The result is a mess of dissatisfaction and half-bakery. Nothing is ever finished or fully right. It also, maybe paradoxically, leads to systems that feel less under your control.
Systems like TinyCore and Live CD distros take a different approach that the OS is finished. You have two choices, take it or leave it.
Unless you are prepared to cross a non-trivial barrier to remix and update the non-volatile image, you are forced to just use what you have. That leads to more productivity because you adapt to the tool rather than constantly adapting the tool to you.
I like TinyCore because it's looking to a middle ground of baking immutable systems at key stage points and keeping changes separate from the immutable core. I can change the core if I want to, but rarely.
I see that as a separate prospect than "appliance platforms" like Android and a PhoneOS onto which you can only load "apps".
What ideas and favourite solutions do other's have for using immutability, or not liking it?