The thing I have a problem with CFL's is their failure rate. A couple years ago, back when they first started showing up everywhere, I saw them as a nice little long-term investment so I jumped into them whole hog and started replacing them all over the house. Unfortunately I had many failures. Mind you, this was when they still cost $5-$10 EACH). When you pay $10 instead of $1 for something that is going to take YEARS to pay you back, having it fail in 6-12 months is a BIG money LOSER. (And most certainly worse for the environment) You also can't put CFLs in some locations, such as light fixtures that are enclosed, because the heat build-up will cause them to fail in short order.
Personally, I'm waiting for the price of LED replacement bulbs to come down, though I'm sure they would be susceptible to failure under the same circumstances. Some LED replacement bulbs even have active cooling (i.e. a little fan) which adds even more complication and opportunity for failure.
I just found this, it's two years old but interesting: http://www.theregister.co.uk/2009/06/01 ... hancement/
Make sure you check out the link at the end of the article to the University of Rochester.