I always hear orks are for fun, not for winning. And yes, when I am losing I can have just as much fun, if not more then when I am winning.
However, with a high powered Warboss and retinue ( 7 models, around 350 points) and basic troop choices + powerclaw and Iron gob ( +1 leadership) I found Kult of Speed to be quite a pain in any Chaos player's rump.
Its all in the sacrifice, give them one squad or two, set up for the burna boys by sacrificing a squad or two of trukk boys.
My army list has 8 burnas in it, 1 squad of burna boys, 1 squad of skarboys with 3 burnas.
Orks are so cheap in points I field about 40 orks, a high powered hq, battle wagon fully juiced, looted leman russ, and a big mek with retinue shooting the 4 bolt on shootas on the battlewagon.
Sacrifice is the key word, give them the lesser squads to set up for orky shooting and more brutal squads.
More power weapons and powerclaws the better, as with any army
A Kult of Speed army can have up to 11 burnas, 5 in a burna boy squad ( mekboy can carry one at hvy point cost) 3 in skar boys and 3 in 'ard boys.
Zzap gun on the battlewagon is key, 2d6 str autohit, then add 2d6 for armor penetraition.
I dont win everytime, but I haven't had a battle that wasnt at least close in a long long time.