The rocket shares 10 sec cd with all activated trinkets. It is an instant cast and 45 yards range, very useful to keep ppl in combat. Boots, parachute, wormhole, etc. = awesomeness, you will notice them way more than whatever static dmg increment you get from other professions.

There are posts in elitist jerks about the value of engineering once you are willing to use/track all the abilities and cooldowns (which is a pain). Short story, eng/jc = optimal combo.