There's other dynamos available, check in NEI for Dynamo, they require more work to be used but they produce more RF, the real problem is you can't feed energy cells power created by any engines that aren't part of Thermal Expansion anymore (they produce MJ, the Thermal Expansion cells require RF to work), which is a real problem. At least, the cells can be used to power stuff that require MJ, I've tested with a few machines from Binnie Extra Bees/Trees and they accept the power from the new energy cells if connected with a cable...
But I agree that we should have the choice on what kind of power can be accepted in the cells, running a 36HP steam boiler from railcraft without anywhere to store the energy, it will be such a pain in the ass...