Nah, that's an exaggeration or someone may have been getting you worked up. Sure, some go too fast... but the majority drive just fine. 1000's upon 1000's of routes traveled every day... these people know what they're doing.
OTOH you could find plenty of stories of unhinged shuttle drivers going way over the speed limit to meet the company's deadlines... take your pick. Mine happened with one of the more reputable companies.
Caminoetas are fine, but for anyone who is truly (irrationally) terrified of travel in Guate, the only option is a private driver.
