CFLs are awful in so many different ways: buzzing, slow to reach full brightness, crappy transformers that burn out too early, etc.

I installed a bunch of LED replacements for 60W halogen reflector downlights (Cree LR6's). At $70/ea, they were unquestionably pricey. The rationale for the expenditure was that we hated CFLs and halogen bulbs were putting out so damn much heat that it was uncomfortable to sit under them. That problem is now completely solved for me, but I imagine the price needs to be more like $30 before most consumers will take the plunge.

Similarly, current-gen brand-name MR16 LED lights are $25/ea (and the uber-awesome ones are $70/ea) versus $4/ea for brand-name halogen MR16's. If they can get the price down to, say, $16/ea (4x the cost of a regular bulb with easily 10x the service lifetime and 10% the power consumption), and they make them compatible with electronic power supplies and dimmers, then I expect they'll go flying off the shelves.

EDIT: when in doubt, find the appropriate nerdy lighting forum's thread on the new Cree LED. The new Cree LED module, all by itself, is $18.67/ea, quantity one, down to $9.30/ea, quantity 5000+. Sounds like they're targeting $30-40 per finished bulb.