The best thing about the ZX81...
...and the ZX Spectrum wasn't the hardware. It was the manual that came with them.
In both cases, the manuals were absolutely excellent, perfectly pitched at the total beginner, whether young or old. Even as an 11 year old kid with no prior programming experience, and nobody available to go and ask, you could pick up everything you needed to know from those excellent manuals. By comparison, the Commodore manuals (along with their BASIC language) was quite poor. Later I ailso got an Atari 800XL, and the manual for that was frankly pathetic, being about 20 or 30 pages long. The Sinclair manuals were hundreds of pages.
The combination of the quality of those manuals, and of course, the (relatively) affordable price of the hardware (£100 was a fair wedge back in 1981/82, especially with 3 million of Maggie's minions un-employed, as was my Dad) is what helped to foster a generation of back-bedroom programmers that still work in the industry today.
And while I'm in a praising mood: Teachers. I remember my secondary school teachers at the time, 82, 83, 84, 85, being just as addicted to these new home computers as us kids. They facilitated after school computer clubs, scrounging TV sets from around the school, bringing in their own computers, encouraging us to being in our machines, demo the programs we had written, help to teach us new techniques, and even learn from us.
When we weren't all playing games, that is :-)
What marvellous, lovely teachers they were, and how lucky I was to have been born in 1970, at the perfect age to take advantage of the home-computer boom.
Looking back at the early 80s Britain, there wasn't all that much to be cheerful about: Miners strike, Falklands war, 3 million on the dole, etc. especially for our parents, but for us kids that were in the right place at the right time, it was a golden age and I wouldn't swap it for anything.
Oh, and the music was better ;-)
Have a good day, all.