fully upgraded you get 15 seconds on & 15 seconds off (15 sec cooldown) & as far as speed, I am almost positive that it is equal to rank 3 speeder piloting. I too was skeptical, but after purchasing them, I find that they are a godsend.
Hmm... I think I might try them then. One more question: do they deactivate after being attacked? (Like how you get knocked off speeders when enemies start attacking you.)