This procedure works excellent with ampicillin as a selection marker.
With kanamycin or streptomycin transformation rates are ten times lower.
With chloramphenicol as a selection marker this method failed in our hands
For more information see:
Brian Pope and Helen M. Kent
High efficiency 5 min transformation of Escherichia coli
Nucleic Acids Research 1996, Vol. 24, No. 3, 536-537