KDP select. Does it work for you?

I have enrolled my books into the KDP select programme.
The basic incentive behind this programme is for Kindle to have your book exclusively. This may seem daunting to some author's; it did to me at first. However, I decided to enroll my books into the programme on a trial basis. You are tied in to the programme for 90 days, but after which you can opt out. I guessed it was worth a try.
When you enroll a book, KDP allow you to promote your book for free on any 5 days you please. I chose to seperate my 5 days over a few weeks, some author's choose for a 5 day run. I had virtually zero sales when I first uploaded my book. On my first day of free promotion, my sales rocketed to nearly 200. The next few free days, I watched the sales soar to into the 1000's. Obviously I didn't recieve any revenue from these free sales, but my sales ever since have been steady. With that, it would seem that the free promotion has aided my books exposure and sales.
The other benefit from the programme, is that the book will be available in the Kindle lending library. Kindle has a monthly kitty of roughly $500,000. If a book is borrowed from the library, then the author will recieve a share of the $500,000. This to me is what bent my arm into submission. After the first few weeks, none of my books had been borrowed. I was beginning to think I had made a wrong decision. However, my books pulled through and my first borrowed report came in. Working out how much my book is borrowed for with Kindle's estimated calculations, state my borrowed book earned me $5. Not bad considering the revenue I usually earn from that book is only $0.60. Since the first lending, I have subsequently lended another 5 books. That's $30 in total.
The KDP select programme doesn't always work though. I have had one book that has lay stagnant in the lending library. I have hardly recieved any free sales in comparison and no borrows what so ever. The game we play as author's, regarding self publishing is that it is definately a game of luck. It is down to us to promote our work and us alone. KDP do nothing to promote our work unless it reaches the top 100 list. I do believe that the share of $500,000 is a good incentive, but if my books were on other sites such as Barnes&Noble, would I have accumilated the same revenue anyway?
In conclusion, the programme works for author's in the same way a bet works for a gambler. It can go in any direction. I have found success with one book and misery with another. The upside to my stagnant book, is that after 90 days I can publish it onto numerous sites. I have opted to do this with my other books, even though they are doing well in the lending library. The key to self-publishing success to me, is the exposure. Having my titles on Kindle alone, doesn't get my name noticed by people who don't own a kindle. Hopefully by uploading my titles to many different websites, I will increase my visibility and therefore sell more books.