We use him living area (kitchen table) and are very satisfied. Subjectively, they are a little brighter than the about 5 years old halogen spot that we had so far in it. But that may be due to the age of the old radiator.
The spotlights are immediately (which does not mean that these 0.5s delay would interfere with other LEDs myself). A special transformer I do not use, it is the same who has previously operated the 3 halogen spotlights.
I recommend to order several at the same time if they are to be used together, because apparently fluctuations in production on the light color have influence.