From the Kindle point of view - I'd say it's a definite yes. Worthwhile from the point of view of personal satisfaction, from hopefully gaining some more readers, and from making ... some pocket money. As I've said already - I didn't do this in the hope of becoming wealthy, so I haven't been disappointed! But then again, I'm pretty realistic about such things, having been published for quite a few years in the traditional way and never having become anywhere near wealthy from that either!
I'm really glad I got 'on board' with Kindle just as it was really taking off. It's been an exciting experience. I've loved the feeling of being in control of my own destiny - of being able, within reason, to set my own prices, to experiment with reducing them and even offering free promotions, and watching the sales figures and Amazon rankings to see the effects. None of this was possible with a traditional publisher - the decisions were out of my hands, and I only found out what I'd earned every six months when I got my royalty statements.
The free promotions, which you can do by joining KDP Select, have I think definitely been worthwhile. Some authors don't like the concept of offering your work free, and up to a point they're right ... ebooks may not have a physical production cost, but my books still represent about a year of my hard work, and who would be prepared to work for a year for no pay? Yes, it irritates me when readers say they don't expect to have to pay for ebooks at all (?!) or that they refuse to pay more than the absolute minimum (so maybe they lose out on some of the best books?). But a free promotion of just a couple of days - you can do up to five days at a time with KDP Select - is an interesting experiment. The first time I tried this, I watched in amazement as about 1000 copies of the book were downloaded in a day, even in the USA where my books don't usually sell so well. All free! But the point is, none of the people who downloaded it free were ever going to pay for it. And having read it, they might well go on and buy one or more of the others. AND, the biggest surprise was the increase in sales of the book during several weeks AFTER a free promotion. So I've done several more since, with different books.
The most annoying problem I've encountered with KDP is the way royalty payments from the USA are made. The UK payments, as long as the £10 threshold has been achieved, are paid into my bank account every month and that's great. But with the US earnings, you have to achieve a threshold of 100 dollars - which took me a while, because I sell far less books over there than in the UK. And then - the only options are payment into a US bank account (needless to say, I don't have one and couldn't use it if I did), or by a cheque in US dollars. When I got the first cheque of just over $100 I was pleased ... until I tried to pay it into my bank. The bank charges are so high, for a relatively small cheque, they refused to handle it. I tried other banks - discussed with other people - all agreed it's a real problem unless you're earning bigger amounts (in which case the charge is a smaller percentage of the amount). I ended up asking Amazon to void the cheque, and hold my royalties until they mount up to something more worthwhile so that the bank will agree to handle it. I also asked them why they won't consider paying by PayPal or even payment into my Amazon account. (Surely that would benefit them too). They pretty much told me to 'watch this space', but nothing has changed. So I've not received a cent yet from the USA ... and to think I went to all the trouble, including a trip to the American Embassy in London, to get myself certified for not paying US tax!!
As for CreateSpace - it's really too soon for me to say whether it's worthwhile as I've only just created my first paperback with them. I'm pleased with the finished result, although the cover is a bit flimsy. The paper is good quality, the print is good and clear. But I'm not sure whether it was such a good idea to produce a trade size paperback, as a mass-market size would presumably be cheaper and attract more sales.
So far my sales have been minimal but I didn't expect to sell in shedloads and that was never the reason for doing it. The royalty is poor, but then again the service is free so it's hard to be too critical of that. Kindling is also free, easy to do, and the returns very much better so I don't think there's any doubt the ebook is the way to go for self-publishers. But to give your readers a paperback option too, CreateSpace makes it possible and relatively easy.
The most annoying thing with CreateSpace was that author price copies are currently only available from America. By the time I'd added shipping costs to the price of a reduced copy from the States, to say nothing of waiting for it to arrive, I decided I might as well pay full price from the UK website - but I'm not happy about it. I took this issue up with CreateSpace, and their reply was:
'Member orders are currently printed in the U.S. We understand that improving shipping time lines and cost for our international members is important and want to assure you that this is a priority.'
The point, for me, is that until or unless I'm able to order author price copies from the UK, I will not be buying a stock of books to sell myself. This is a great pity, as I normally sell a few books whenever I give a talk, and could have offered copies of this book for sale if I could have bought them at a slightly reduced price. To buy a quantity, at full price, with no guarantee of selling them and no chance to offer anyone a slight discount, is just not worthwhile.
With either option, as with any self publishing (and indeed even if you're traditionally published, nowadays), the promotion is all down to us, as authors - and I've tried to tread a fine line between telling people about my new editions via Facebook, websites, author newsletters, etc - and irritating the life out of everyone by overdoing it - bombarding them and talking of nothing else. But you obviously do need to make readers aware, somehow, of what you're doing!
Despite everything, if I get the opportunity to be published by a mainstream publisher again, and the conditions are right, I'll still go for it. In fact the rights of my most recently traditionally-published book, 'Tales From a Honeymoon Hotel', are still with my publisher and they are planning soon to publish their own ebook version. I'm going to find it very interesting indeed, comparing its progress with that of my self-published Kindle versions of the other two titles in that series.
But I'm really pleased I've had the experience of self-publishing, now that it's so much easier, cheaper (or free) and more 'respectable'. I've definitely enjoyed it and will be doing it again. Good luck if you plan to give it a go yourself, and I hope these posts have helped a little!