The "LED" part is simply the backlight source (versus the more common CCLF fluorescent tubes). They get to full brightness nearly instantly, last longer, use less power and don't degrade over time as much as the CCFLs do. They can also be packaged into thinner screens. The actual pixels are still produced by a thin-film LCD, same as current screens.
The ultrafast response times quoted for many "gamer" LCDs are for lower quality TN or MVA panel technology. Bright and fast, but poorer viewing angles and less accurate color and greyscale.
High quality PVA and IPS panels tend to be slower but far superior in image quality (viewing angle, gamma, consistency, etc.). Besides, 14ms is likely to be fast enough for all but the most serious gamer (who wouldn't be buying an Apple display anyway for $900).
However, I do have to say that I believe the DisplayPort-only connection was a poor choice on Apple's part. And why wouldn't Apple release a 20" equivalent display? Sure, the 24" is nice, but what about people who don't want to spend $900 on a display to go with their new $1200 laptop?