What about old LORETA?

Previous to the development of sLORETA, the linear, distributed tomography of choice was LORETA (plain, non-standardized low resolution brain electromagnetic tomography):
R.D. Pascual-Marqui, C.M. Michel and D. Lehmann, Low resolution electromagnetic tomography: a new method for localizing electrical activity in the brain, Int J Psychophysiol 18 (1994), pp. 49–65.
At present (2007-February), this paper has been quoted more than 500 times.
That first LORETA version had achieved low localization error, but not zero. If your aim is the correct localization of human brain function, then old LORETA is obsolete, as compared to sLORETA.
The first LORETA version has been validated theoretically and empirically. With sLORETA, things can only get better.

Get back (to) LORETA