Nothing beats an RC boiler for efficient fuel usuage over long periods of time. Once it heats up, even a pathetic 1LP boiler beats anything GT has to offer as far as I can tell.
That said, for power-on-demand, the GT Boiler suddenly shines a bit. It heats up stupidly fast and creates a correspondingly stupid amount of steam very quickly. But its fuel consumption rate is pretty alarming.
Well, you guys have convinced me. It looks like I'll be building a GT boiler in the near future.
Any hints for how to keep it from blowing up? I made a setup in creative where a liquid detector on a GT pipe senses the incoming water, when the pipe goes dry (which should mean something like >16 buckets left between the internal boiler tank and the pipe slosh) it shuts off the ender io conduit feeding fuel. I just worry about the stack of fuel (like coke) in the boiler being able to use up all of that water....