It is extremely dangerous to use: it utilizes so much power than any mistake could release thousands of megatons of destructive force. Continuous use has the risk to make the engine explode, and turning it on and off risks cutting off the connection to the Null Zone making it even more unstable.
Despite it flaws, the Negative Drive is by far the fastest engine in the Olympian Galaxy.
First appereance (prototype): Beyond The Impossible #60
First use: Beyond The Impossible #169