Huraah!!! I have finally replaced the last incandescent bulb in my house. The reason I took so long is that it was connected to a dimmer switch which have been a real problem for low energy bulbs. Homebase have finally started selling dimmable low energy bulbs made by a company called Varilight.
The bulb was a lot more expensive than an ordinary low energy bulb (£11.99) but I had wanted to replace the incandescent bulb for a long time and I expect the price will start to drop sooner or later. The bulb works pretty well with the dimmer although it take a significant fraction of a second to adjust so if you change the dimmer to quickly the light increases or decreases in sudden steps.
Overall the bulb is good but I think the price needs to come down before they'll really start selling.