We bought our first one of these lights a couple of weeks ago and have tried in a two different places where the light is switched on and off a lot - something not recommended for the cheaper 'green' lamps (CFL). There is a fraction of a second delay between throwing the switch and the light coming out - but it is so small many people will not notice it and unlike CFL's, it is the full light level event quicker then tungsten lamps. Although this lamp is sold as a 60W replacement, I would say that it is a bit brighter than the 60W lamps we used use.
Since its light output is biased to 180 degree unlike the traditional tungsten lamp of old which was practically 360, it worked particularly well in the stair well where the light needs to go down and out to the sides to light the landing clearly. A pleasant surprisingly warm light colour, better than many I have seen in the past.
Although the notes that come with the lamp say not to put it in an enclosed light fitting such as those typically found in the bathroom, I have do so anyway - it fitted okay. The reason for the warning is that all of the LEDs have cooling vanes for the electronics which can get warm/hot when the lamp has been on for any length of time. In our case, we know that the lamp in the bathroom will not be on for very long due to the way we are. Being the bathroom, the light does get switched on and off a lot and so the LED suits the function quite well.
I would have thought that it would pay the manufacturers to produce LED bathroom fitting because they would suit the function really well - fit and forget. (Well... until the Mrs's decides on a change!)