Ok, my input, for what it's worth.
I've recently been playing the tekkit mod on my server at home, and the 1.0.0 additions make geothermal quite significantly more useful as a form of long-ish term mobile power.
I'll take a stroll to the nether with a fire-resist potion and a couple of stacks of cells, and wander around a lava lake for a few minutes, until they've all filled up. Then, two geothermal generators topped up with about 20-30 cells apiece will power a diamond-OV miner away from my base, for it's entire cycle.
Now, I've not been too fussed about nuclear at the moment because of it's high initial cost and because, the way I prefer it (i.e. completely unattended, with no risk of explosion) it just provides a moderate source of energy for an extended period, which a bank of about 15 solars on the side of my house do quite happily, and will keep me going for the forseeable, or until I get bored with the buildcraft side of things and come back to play around with the IC2 stuff.