Here are reviews of retrofit halogen energy savers. Brief descriptions + my personal, subjective impressions of how they look in my home environment. (Note: prices are converted from SEK to Euro, include 20% VAT and may vary between countries.)
* 28W Osram E27 clear A-lamp
Info: CRI 100 (= full colour rendering). Costs about twice as much than its incandescent equivalent, uses about 20% less energy (though advertised as 30% less) and lasts twice as long.
Impression: Looks exactly like the 40W incandescent equivalent it’s supposed to replace, though slightly brighter and with a rather glaring light point so best for luminaires with a shade.
* 28W Osram Spot R50 E14 reflector lamp
Info: CRI 100. Costs only slightly more than its incandescent equivalent, uses 20-30% less energy and lasts twice as long.
Impression: Looks exactly like the 40W incandescent it’s supposed to replace. And when I say “exactly”, that means exactly and not “more or less similar”, since halogen is an incandescent light, only concentrated into a smaller inner bulb.
Update: Using near the front door turned out to cause too many vibrations for it to last very long.
* 30W Philips Master Classic E27 frosted A-bulb with infra-red coating and integrated transformer
Info: A low-voltage retrofit lamp that can be used in a standard mains-voltage luminaire. CRI 100. Costs over 10 times as much (€13) due to the built-in electronics, but then it lasts 3000 hours, so divide that by 3 and then deduct the 50% electricity savings and it’s not so bad.
Impression: This one too gave a nice warm-white incandescent light that looked bright enough to replace a 60W bulb, as it promised. I could not tell it apart from a standard 60W frosted bulb.
Update Dec 2011: I’ve not used this one very much at all, just as a desk light on those few occasions when I’ve worked on something not on the computer. Yet one day a few weeks ago it just died. I have definitely not used it anything close to 3000 hours. And this is the only type of incandescent bulb that will be permitted in the future, if the European Commission doesn’t change its mind. (OK, one bulb does not make a proper consumer test, I could just have been unlucky).
Update Jan 2013: This lamp was taken out of production and Philips has no plans of ever introducing it again.
More lamp descriptions can be found on this site: http://lightbulbmarket.blogspot.com/