I did some quick testing of the steam boiler today with 545. My test setup is basically Liquid Heat Exchanger -> Steam Boiler -> Steam Turbine -> Kinetic Generator.
Prior to today I was getting about 60EU/t from 200HU/t and occasional steam explosions as the turbine just couldn't keep up. Meanwhile a stirling generator would happily provide 200EU/t without issues, for a lot less cost.
Today, I'm very happy to see that I get 320EU/t (per 100HU/t) and no more steam explosions. The stirling generator now provides 50EU/t from 100HU/t, which is inefficient and I'm okay with that because it is so cheap.
I'm glad that steam is a much more efficient way to generate EU, but it's not perfect yet.
The power output comes in pulses because the turbine consumes steam faster than the boiler can make it, which leads to a brief "dead time" between operations. It would be really neat if the turbine had a speed-up and slow-down, consuming more steam per tick as it speeds up. That way it would become eventually become balanced with the steam input rate.
Much worse, the system can be exploited. Heating a boiler with an Electric Heat Generator creates more EU than it uses. A positive feedback loop, free energy, of roughly 200EU/t. Well, not actually free because the turbine will wear out.
I noticed the heat capacities and heat of vaporization haven't changed, so I'm guessing the balancing is far from done. I just wanted to let Thunderdark know that he should make sure EU generation is never more efficient than 1EU per 1HU, or whatever the Electric Heat Generator's ratio is.