pHarmacist: What I meant was that alkyllithiums are less chemically selective, and that you cannot automatically use a R-Li when a synthesis calls for R-MgX (there are more added dangers too, but that wasn't my objective).
Organikum: As long as you aren't breathing/touching the ammonia, the birch reaction is extremely simple. You just have a container of ammonia, add an alkali metal "plop, plop, fizz", then add your aromatic "plop, plop, fizz", let the solvent evaporate and you have your product. No big deal. But a grignard reaction is comaratively involved.