I love my Oyster subscription!
My only complaints are that it isn't e-ink and they need more customization in their apps. My iPad Mini and Kindle HD 6 make a great format size for reading apps.
I have been using it for 6 months now and have kept a spreadsheet to evaluate the costs. The average price of my books borrowed is $8.67 and the median price is $9.99 (not very shocking since I read mostly big publishers and mainstream bestsellers). Of the 26 books that were borrowed, only 3 were also in my local e-library and 6 were in Kindle Unlimited. Overall, I have had a net savings of $175.41 after deducting the cost of the monthly service from the Kindle price of the books. Therefore, it is worth it for me!
I agree with the original linked article that I am more aware of publishers now. The selection is amazing on Oyster. I have enough books wish-listed to last for years. I love the way the app is setup for recommendations and similar books that it increases discoverability of other books that you can add to your reading lists. Your reading lists are like collections so you can easily keep track of books to be read.
If you like to re-read, then it's no big deal. You just borrow it again from your finished list. There is no guarantee that it will still be available. So far only one book that I have read was removed from the service. They gave me a warning that it would be expiring before-hand. Everything else is still there.