Thanks, @dedicatedguy for your input.
I don't think it would be great, because controlling them would be very difficult and they will surely hunt us down :P
In some culture, dragons were said to be intelligent because they need to outsmart dragon hunters. I mean come on, all it takes for us to conquer would be to kill one of them, make a fire-resistance cloth out of their skin, maybe some weapons with whatever they have and poof, suddenly dragons would be at the brink of extinction.
P/S: Most of the dragons love to sleep in a cave filled with glittering stuff like golds so it would motivate dragon hunters to kill them and grab their gold.