Personally… I found the whole magic gear thing a pain. Like Des said, you fart around with stretched chains, only certain cogs, trying to match rings and cogs etc. It was easier to just stick on a tensioner.
I did use a half link on a fixed conversion when the chain stretched a bit and wouldn’t fit. But that all changed when I bought a new bike. 
i run a shadow conspiracy half link chain on my bmx.
it is a bit heavier than a regular chain. i dont know the exact difference though.
the stretch in it isnt as bad as the first versions of these chains.
it does however eat up my drive train. ive had my tree sprocket for nearly two years and it has only shown wear since running a half link chain for the past two or so months.
i wouldnt run one any other bike except my bmx, and i wont run one on my bmx again either due to the drivetrain damage it does. much easier to get a regular chain and put a half link in it.
yeah thats crazy, tree sprockets are basically indestructable. Do you think that wear would be more from a chainline issue when running halflink chains? or would it be regardless?
I really wanna swap my 30t tree sprocket for a 33t or change my odyssey cassette driver so i can ride my bmx again since the gearing is too easy after riding fixed on harder gears for so long.