Excellent build quality and look very smart. I have normal Halogen spots in various places in the house, and they consume quite a bit of electric, get very hot, and seem to blow regularly. These LED spot bulbs answer all those questions, consuming some 85% less electric, do not get excessively hot and have a life expectancy of 15 years.
This is the 4W (equivalent to 35W) warm white (2700K) version. It's incredibly bright, don't look directly at it. I would say it's brighter than a 35W Halogen, but the light beam is more focused, so you get much more of a `spot' compared to Halogen. The warm white is a yellower shade than normal halogen spots, and are the ideal replacement for the existing standard Halogen bulbs in my bedroom, I found it too yellow for the living room.
They do dim, but I'm using a standard, cheap and cheerful dimmer, rated at 60W min, I tried dimming with a 6W and 3x4W LED bulb (so 18W total), and it only dimmed on the first 5 clicks of the 15 click range, providing 5 big steps from very dark to full bright. Adding two 50W Halogens to the same 4 spot rail, the dim range increased to 7 clicks, indicating the LED bulb load was too low for the dimmer to work correctly. I probably need a more advanced dimmer, but these are generally quite expensive.
This bulb claims to have a better dimming range, compared side by side with the older bulb, but still using the cheap dimmer, I saw no difference in dimming performance.
All in all, a great bulb, especially for bedrooms where the colour is right, but remember to consider the still limited dimming.