Well so far the rocket boost seems to have a fail rate of 50% and had the stats removed from it, there seems to be no need to use it as it could kill you in raiding, and in pvp they are disabled so whats the point of that enchant?
The grenade hits for minimal damage on a 6 minute cooldown and can ruin rotations if you have to click it and move the aiming reticle around.
Head enchant = also useless in every situation, cant mind control anything in pvp and in pve just useless trash and its disabled in pvp as well in cataclysm.
Every other profession has benefits engineering was the fun profession now its more of a gimp profession,chance to fail/kill you and you put loads of money into it and get no rewards where as other proffesions make over 10k gold just from one item...
Seen the new cata stuff and they are equally worthless.
/rant off