Thought I would give a little update.
I now own two M42 lenses, the 50/1.4 (8 element) and a Tak 135/3.5. I also own two m42 adapters, an official Pentax one ($90AUD) and a cheaper $10AUD chinese one with the disassembly tool (I paid $10AUD for it as it was local aus stock with a quick turnaround for postage).
To begin with I had the Tak 50 and official Pentax adapter. People were right that you could unhook it fairly quickly with finger/nail, however the unscrewing of the lens just takes too long for event work, so I removed the spring from the official adapter and just screwed the lens on tight to it (no glue). This is enough to hold things in place, and when rotating the lens+adapter in place, although it doesn't 'click' it still feels like it tightens up its grip at that last twist, enough to feel confident it would not untwist and screw off. Its basically a really nice snug and tight fit where I feel comfortable to use it like that, which means it dismounts quickly for events as well.
Incomes the Tak 135 and the cheaper m42 adapter. Nothing wrong with the lens here, but man the adapter is bad, even when clicked into place (spring included) it just 'wobbles', and once you screw the lens on you have as secure but wobbly lens, it makes aperture changing awful, focusing horrendous, that lovely smooth barrel that they are known for having just goes right out the window...
So I took the spring off, and now the lens + cheap adapter won't even bit or hold in place at all, it would literally just rotate out of place with no force whatsoever...
These adapters are night and day difference, and that really saddens me, because it appears a good adapter is an expensive one which in turn then increases the price and value of these cheaper lenses. I possibly overpaid for the tak 135 in the first place ($110AUD), to spend $90AUD again just to get a good adapter makes its appeal drop massively...
I don't know if all m42 adapters are like this, or just that I got a particular bad one, but I can't continue to shell out $4-10 constantly hoping to land a good one...
Such as shame, it's actually really put me off the idea of investing in more M42 glass...