Oyster and Scribd have done similar services; I was one of the early adopters of Oyster, and while I loved being able to grab a book while traveling and read on my phone, I eventually let it go. I am a Kindle lover. I have an iPhone and an iPad, but most of my reading is done on the Kindle (the old school keyboard one). So, as a reader, Kindle Unlimited lets me binge read on my preferred device.
The other advantage? As a writer who indie publishes, Kindle Unlimited has opened a whole new door for me. I have run Kindle freebie promos and have been in the Kindle Prime Lending Library for a long time, but I'm getting more Kindle Unlimited attention than I could have guessed.
So, if you love your Kindle like I do (or just love the Kindle app), give the free month of Kindle Unlimited a go. I'll still be using the two freebie days I have left soonish for those of you who are not KU members or who want to own a free copy without having to return it on loan, but I think you'll find the $9.99 a month is worth it if you're an avid reader of eBooks.
The other game changer (potentially) is that in the battle between Hachette and Amazon fell out this lovely little golden egg for Indie writers--We will now be able to have a pre-order button!
If that's not enough to get me off my butt and write more, I'm not sure what is.