We've been trying some of these new lights.
http://www.lightology.com/index.php?module=prod_detail&prod_id=332815&option_id=332814The problem we've encountered in the past with LEDs, particularly for these specular reflector lights has been the color and color rendition. For my eyes, in a residential setting, we want something around 2500K-2700K (warm white, or very warm white)) and the highest CRI possible. The CRI on the original quartz halogen (20w) lamps is 100; pretty hard to beat in a kitchen where you might like to have oranges look orange and tomatoes look red.
These are 7w, dimmable, 2700K and 95 CRI. They replace the equivalent of a 40w incandescent. I'd say they are very comparable to the standard 20w BAB's. Great colar & CRI and they dim smoothly down to ~5-10%. We regularly use these on a 12VDC track - just wire the terminals so they both go to the low voltage conductor strips, usually they are both on the same side. The lamps are a bit pricey, but the "gimble rings" are dirt cheap and readily available. Lots of low voltage fixtures they'll work with. On a dimmer they make excellent reading lights. Very good for displaying our boys latest "art work".
They are also available in 7.5w; a bit more light. Only slightly lower CRI.
~ks