The boiler can accept heat from any side, but any more than 480 (ish) causes the boiler to heat faster than the water, and the boiler explodes at about 250 C (ish).
The fluid regulator can now work in speed/tick or speed/second. Meaning 1 bucket per tick fluid transfer 
RPT is gone, and now the Kinetic Steam Generator just makes kU.
Coolant is now made from either 1 lapis dust and 1 bucket of distilled water, or 8 lapis and 1 bucket of normal water.
Plenty of bugs fixed, many of them mine 
We're still waiting for the super heater to make super heated steam.
The pump has changed, but still isn't relevant to the reactor stuff, apart from maybe filling a canning machine up with water 
Pretty sure that's about it