The steam inserters move much slower than they are supposed to.
First I tried changed the maximum_temperature from 280 to the 120 degrees that the boilers output. That didn't help.
Next I unset the fluid_usage_per_tick to let the game auto-calculate and now they work as expected.
I haven't tried putting the maximum_temperature back to see if it still works correctly.
If you update this mod for 2.0 please take a look at this.