I like BC-IC2 Crossover mod, simply because they are engines that instead of using coal or oil or fuel to power themselves, they use EU as their fuel, And its only logical that the higher tiers of generators should overheat due to the massive amount of energy they produce and pump per revolution.
Its a mix of both IC2 and BC instead of just being IC2 on top of Buildcraft.
And one thing i would like to add, its that i actually hate how conversion has been going in a 1:1 ratio, being a good follower of the church of balance i still think there should be a 5 or 10% power loss during energy conversion (but thats just me).
Oh don't get me wrong, I think Silentdeth's implementation is outstanding. It manages to maintain the flavor of both.
Forestry is also a very nice hybrid. It works by itself, with BC, with IC2, or with both, but you get to the most out of it with all 3 mods installed. That in and of itself makes it awesome.
I still would like to see a straight IC2 on top of Buildcraft (transformer that outputs Mj) although BC is starting to grow on me too.
I agree about some (not necessarily the amount) loss but bear in mind there already is loss; you need to provide and power a pump.
So the heat production is your loss.