There are a couple of RGB color spaces out there - LStar-RGB.icc and ProStarRGB.icc- that use the L* tone response curve. What's the supposed advantage of using the L* TRC over using a gamma curve as the TRC?
The intention behind L* was to make for a device independent colour space with a more neutral or 'flat' representation than available with Adobe RGB or sRGB. This is done by replacing the gamma with a set of calculated luminance values for the grey axis.
The L* colour space is said to exhibit less compression or blocking in when you make changes such as applying an S-Curve to increase contrast.
Colour guru Dan Margulis seems keen on L* (certainly over Adobe RGB, sRGB and ProPhoto RGB) writing:-