Even the cheapest compact fluorescent light bulbs are good for general lighting. With the cheap models the quality of the light is not always quite as good as with ordinary light bulbs, but this is still just fine for general purpose lighting. For reading and other tasks where you require good lighting conditions I recommend a little more expensive energy saving alternatives which will be discussed later.
Compact fluorescent light bulbs are more fragile than ordinary ones. Especially when hot they can break quite easily. Therefore it is not a good idea to use them on lamps which you will move or you might accidentally hit. On the other hand, the longer life makes them ideal for places where the lamp is difficult to reach.
Switching the light on and of will make the bulb wear out faster than having it on continuously. Therefore I don't recommended using compact fluorescent light bulbs when they will only be used for short periods at a time. As the lights are not used for long, the energy savings are not that big either, so you can just as well use ordinary light bulbs. In addition, compact fluorescent light bulbs are more efficient when they operate for several hours at a time (2 hours or more).
This article from Treehugger.com addresses the issue of when to turn lights off and when it is better to leave them on. Here's the short version:
"The rule of thumb for optimizing the in-use versus turn-on power is:
Most energy efficient lights bulbs should only be used in moderate temperatures indoors. If you wish to use
energy efficient lighting outdoors, make sure you buy light bulbs that have been made for outdoor use. Similarly, most compact fluorescent bulbs are not dimmable - if you are using a fixture with a dimmer, make sure you buy one that has been designed for that.
Energy efficient light bulbs are really handy if you want to get more light from your lamp, but have reached the maximum wattage allowed. Say you have a fixture that allows a 60W max light bulb. Instead of using a regular 60W incandescent lamp, try using a 20W or 23W compact fluorescent. You will be nowhere near the 60W maximum, but still get significantly more light than with the 60W incandescent.