well mark forge are reall the only ones who are currently doing it properly.

The rest are just using pla with carbon fibres mixed in. Reall doesn't make it any stronger. It's a little more rigid, but also more brittle then normal pla.

Basically it's a gimmick that doesn't really do anything that useful.

Unless you'e got a print service with a mark forge printer - I wouldn't personally bother with the carbon fibre filaments.