I bought my first String Stretcha a few years ago from the maker in the USA. I thought at the time it was a very fine little tool and decided to give it to my guitar technician friend who usually did string changing and setting up for me. He has found it absolutely indispensable as his 'go-to' string stretcher.
I've now got back into changing my own strings so I thought I'd better splash out on a Stretcha of my own. I say 'splash out' because, compared to other string multi-tools on the market, it is rather expensive. But, make no mistake, it really is worth every penny! The American guy who developed it took the basic principle of using your thumb and a finger to stretch the strings and converted it into solid plastic - thus completely avoiding any finger laceration. With a perfect ergonomic handle that fits firmly in your hand it's a joy to use. And, more's to the point, it does its job beautifully.
I don't think one can really recommend this too highly: it's an absolutely brilliant little invention that deserves to be far better known and better available than it is. I believe you can only get it from the American supplier or from Thomann - nowhere in the UK seems to sell it, which is a great pity.
So, to make string-changing and tuning up so much easier do not hesitate to invest in one of these: you'll never regret it - it's money well spent! A brilliant little tool!