Dr. Pepper mentions LEDs not meant for enclosed fixtures being used in them. Most of the cheaper LEDs fit in this category. Most of our fixtures are totally enclosed so I haven’t switched those to LEDs, mostly because I haven’t done the homework to figure out which ones are suitable.
I’m surprised no one has mentioned a major problem with CFLs: they contain mercury so they shouldn’t be disposed of in the garbage. It’s not a big deal, since places like Lowe’s, Home Depot, and Best Buy recycle them.