I have a Anaconda, and i only use 2x type 2 beam lasers, the rest are pulse(inc the huge hard point- type 3 turret pulse)
This is my current trade ship set up,
http://www.edshipyard.com/#/L=706,5...a9Y8SCgD88I,0Bk0AA0AA0AA08c08c08c0724_w7RA03w
yes its a bit excessive with the shield generators, but should anything decide to pick on me, i can fight them off.
I can run all the pulse lasers and get a good 30+ secs of continuous fire out of them, but if i drop the beams onto the target, it just goes zoooooooooom empty...in about 10 secs!
Smaller ships - basically any small size ship is going to massively overheat with a beam laser on it, use a heat sink to offset this.
Medium ones are ok with 1, but 2, is going to give off a load of heat (this includes pythons) so be careful with your load outs, again a heat sink is a viable option for your load out- and can be a game breaker in like vs like ships (they usually have mates) so Nuke em with the beams, drop a heat sink, and nail the power plant.
Pros of the beam vs pulse, they destroy shields like butter
They look very cool in battle

Once the target has no shields, they easily fry the target.
Negatives.
They cost a damn fortune! 20million for a type 3 turret!
They use a VAST amount of power
They create a LOT of heat
Basically balance your ship setup, and use the beams to assist with shield strip, then use them to specific kill the power plant of the target - this gives the target something to think about- heat build up, and getting its ass melted at the same time!
Just run the numbers on ED shipyard, and make sure you can afford to run them, power wise. As the OP said, the high power draw is a major issue, until you get into the Python range of ships, and even then you cant really have more than 2 without seriously giving yourself heat issues