Maybe the Dakkajet is decent for taking out light vehicles, certainly things like Raiders and Venoms. I reckon its much better for taking out infantry and monsters. Will work brilliantly against Eldar, Nids, Orks, DEldar and Guard. Leave the vehicles to the Lootas, Deff Rollas and Klaws. The fact it can out-range most of those opponents makes it even better.
The two Bombas I need to do a little work with to use properly. Cover is their friend for now, try hopping from behind building to building. They'll be lucky to use their bombs, and almost certainly only once. I do like the idea of unloading all of the Skorcha Missiles in one swift strike - I'll have to try that.
Mostly though, these jets are purely for fun. As all Ork stuff should be!