Amazon – a delight or a disaster?

I was wondering how other readers and writers viewed Amazon. Since I started author-publishing in June 2012 things have changed dramatically.
When I first started, preparing your book for Kindle was quite challenging and took someone with low technical ability (like myself) a long time to master. Today the formatting is done for you and a file can be uploaded as word.doc or html – both seem to work equally well. Previewing your book is straightforward and one also has the option to download the file to your own Kindle before sending it to be published. This also wasn't possible in 2010 – I didn't even own a Kindle – I only bought one so I could see my books.
If you put your book in a free promotion in 2010 you could get tens of thousands of downloads and this immediately translated into a ranking figure and pushed your title into various charts – this flowed over into the paid charts when the book came off promotion. Today I don't do any free promotions – people who do report that they are lucky to get 1000 downloads, and this doesn't then reflect in the sales ranking as it used to.
Today there is another option – doing a book promotion where your royalty level remains the same, and you reduce the price as low as you can and then it increases in steps until it returns to the original price. Again the first few times I did this, when it was first available, I got excellent results – not so any more.
Then, from last July, Amazon introduced Kindle Unlimited (KU) a subscription service for readers, and everything changed. From having around 60 or 70 borrows, I was now getting 10 times this amount. Then the UK and other European countries were added and my borrows doubled. As the majority of my books sell at between £1.50 and 73p , the royalty I receive per loan is far more than I would get for for a sale. My sales increased in pace with loans.
This sounds like Amazon's a delight and not a disaster. It certainly has been a delight for me, as my income has doubled over the past four months – and it was pretty good before that.
However, for some writers, both those whose books are not in the system and those whose books are, this has proved a disaster. I have been hearing reports that in some cases book sales have been reduced to a trickle and incomes dropped by as much as 75%. Also the writers who have seen these drops tend to be selling their books at well over £2, and this means that a borrow is less royalty than a sale.
There is often a drop in sales in the run-up to Christmas and first thing in January, but the drop some writers have seen is a downward trend since the introduction of KU.
In the UK VAT rose from 3% to 20% on January 1 which means writers  had to take a drop in royalty of 17% unless they put their prices up. Also it has seen the demise of the 77p book – I'm not sure that is a bad thing.
For me Amazon has been a life changing thing – three years ago I was a relatively unknown historical romance writer and today I can call myself a bestseller. I just hope that things even out for all those other writers who are suffering.
What do you think? Do you think that Amazon is being beneficial for writers or a disaster?
Fenella J MIller