First consider the various environmental impacts of using CFL. I guess around 4 years back an European Union ruling compelled all businesses in EU to dispose of most lamps, including fluorescent types in an environmentally considerate manner. This obligation now extends to USA and a host of other countries as well.
Make sure you install 10% more light than you need as the light output falls off with age, also the light output will not reach maximum until they are at running temperature.
Flicker from CFL lamps should not be an issue when they are new as the frequency at which they operate is around 20,000 Hz, however, as they age the smoothing capacitor in the power supply of the lamp circuit looses its capacity and the 50Hz mains flicker may become apparent to some more sensitive people. The solution is to change the lamp OR run them off 240V DIRECT CURRENT from a battery supply charged by your UPS perhaps.
A regular bulb creates light by heating a tungsten wire to white hot. 90% of the energy consumed by the lamp is lost as heat into the surrounding environment. A typical incandescent (ordinary) bulb has an efficiency of 12 to 15 lumens per watt (12 Lm/w). In other words you only get 15 units of light for every unit of electricity you put in. Now compare this with a CFL. This lamp creates light by exciting atoms of mercury vapour, making them give off ultra violet light. This UV then hits the white coating on the inside of the lamp and is converted into the light we see. Very little heat is produced in this process, giving this type of lamp an efficiency of 60 Lm/w which is 4 or 5 times greater than the ordinary bulb. So a 20 watt CFL will give the same light as a 100 watt bulb at one fifth of the cost (or electricity used and lower carbon emissions etc). You can also use them as Shop Work Lights.
Also, CFLs last about 5 times longer than incandescent. In addition to cost savings you're also saving electricity which reduces the demand for new power plants.
There are those that still argue against them based on their mercury content, but it's just silly. The mercury level in bulbs today is so low as to run no risk to the user. Where it is a problem is when they're disposed of, so the best thing to do is recycle them properly.
So yes, they are worth it. LEDs will probably be the ideal light in the future but for now they have many hurdles to overcome (cost, lack of fill lighting). For at least the next 5 years, CFLs are the way to go.