The funny thing is that I love lava as an energy source, but rarely ever use it, because I tend to have a massive input of coal/charcoal/seed oil, making my early stage quite easy in term of energy generation.
( 3 9x9 farms for wheat, and a turtle managing 20 trees, cutting them down every 5-10 minutes and feeding that into a furnace of some sort).
As some people said, lava is a great source of energy, but it comes at the cost of having to build an infrastructure to be able to automate it, where you could produce other energy sources using stone, redstone, glass, iron and a chest (plus a diamond/gem tool).
Forestry has so many ways to make really decent fuels, peat even doubling as a fuel for normal coal powered machines.
Railscraft can also level up your coal by quite a lot, granted that you spend a little sand and clay, and one of the most efficient uses for your fuels in the form of steam boilers.
The users of DW20 pack also have cheap solar energy for IC2, with normal recipe and compact solar, but the Mindcrack pack comes with solar that can also produce a little during the night.
Oh, and if anything fails, you still can power your BC stuff via RP solar or wind power too.
Damn, now I want all that in my world...