This bulb has an attractive slim shape, slimmer than the equivalent compact fluorescent. Almost instant on (perhaps 0.1sec delay) then virtually full brightness immediately after that. This seems common to LED bulbs. The light is whiter than most eco bulbs, just a little off brilliant white, but not too harsh on the eyes. Light output seems same as about 20W incandescent. Distribution of light is nicely uniform around the bulb, not just out the sides or top. Haven't tried a dimmer switch yet, but hope to update this review once I have done.