I have been trying to replace as many light bulbs with LED equivalents but with varying success. The main problem is the LEDs tend to be whiter, duller and different spread of light than the halogens. This was the first time I have tried to replace a G4 20W halogen bulb and was expecting the same problems, but was amazed to be successful with the first attempt. The kitchen has a number of these G4 20W bulbs under the wall units to illuminate the work tops and so I replaced one. This allowed a direct side by side comparison between the LED and the halogens. The light from the LED bulb was indistinguishable from the halogen equivalent in all aspects of the light quality, such as brightness, colour and the spread of the light on the wall and worktop.
The fact that they have the LEDs are all on one side make them ideal for the light fittings. They were a bit of a tight squeeze in the light fittings as they are designed for the tiny halogen bulbs. The disc just fitted in the holder with some minor adjustments. Note that there are some electronic components on the back in the middle that conveniently fitted in the central recess of the light fitting.
Before I can replace the rest I need to locate where the transformer is so that I can replace it with an LED compatible transformer. Standard transformers have a minimum load which is usually greater than the LEDs on their own. However, there is usually no problem with just the odd LED bulb mixed in with halogen bulbs, especially with the SMD type.
I am very pleased with these bulbs so far, only time will tell if there are any problems.