Retrofitting LEDs in your home
Things to look for when choosing LEDs:
C-Tick
At least 600 lumens light output
Fit your existing fittings (MR16 12v or GU10 240v), or completely replace
Consider:
For low voltage halogens, whether you can use your existing transformer, or completely replace your downlights with LED lamps with integral transformers.
If you are already using 240v GU10 halogens, you should test the light output of direct LED GU10 drop-in replacements. If it is not sufficient, you may need to invest in higher wattage 240v dedicated LED fittings. However, this option requires a licenced electrician to install the fitting.
EMC - e.g. does it cause TV/radio interference. Many cheap drop-in LED downlights cause TV interference, because circuits within the lamp are not shielded or filtered, causing the wiring to act as an antenna which radiates radio interference.
Brand - cheap, no-name $15 LEDs generally don't last very long. Consider Philips / Osram - they are currently the best on market for longevity, light rendition and least generation of radio interference.
When?
You should consider retrofitting LEDs if you plan on renovating or making over your house.
Focus on critical areas of house first, Kitchen, bathroom, onsuite, and take the time to evaluate the performance. Then work on other areas of the house.
Remember that 240v integrated LED lights should always be installed by a licenced electrician.