The anniversary episodes are based on vinyl mini albums released in the 1960's, providing both the story and the voices of the original cast as source material.

Combine that with a modern reproduction of the vintage "Supermarionation" techniques, with real puppets on strings, practical effects and real miniature buildings/props and vehicles, and you get 3 brand new episodes that could easily fit in the original show!

They luckily did not fall in the trap of using obvious green screens or CGI, so the vintage look is very convincing.

The first episode is a bit boring, because 50 years later we didn't really need an "Introduction to the Thunderbirds" anymore, but episodes 2 and 3 are great!

The episodes are also a bit shorter, probably because of the limited original (vinyl) source material, but that happens to also better match with current viewer expectations. I was not bothered by this; it makes the episodes a bit more fast paced.

Sometimes you can tell the budget was a bit lacking, or perhaps experience in using the techniques. For example, sometimes it is quite obvious you're looking at Styrofoam, and not a wall/rock.

Also, the multiple levels of miniatures used to convey scale in the original show is sometimes a bit off in these episodes, where you can tell a vehicle is a small toy instead of a massive machine.

It also looks like they got permission to re-use some audio/shots/sequences of the original show, since this was produced in cooperation with the Anderson family, but that only adds to the authenticity!

Overall, I recommend this for any fans of the original show.