The capacitor that is used to build up a charge in this is low grade. This means that A) nailing into a hard material will cause the nail to not penetrate and B) if you are on a non-dedicated circuit (i.e. other live devices are on the same circuit), using a low amp extension cord, or
I can't emphasize enough that the electricity supply matters. I tried this without an extension on 15A circuit shared with only low-wattage lights and a 20A dedicated circuit and it only worked well on the 20A circuit.
If you are doing light occasional work and willing to use a small headed hammer to finish the few that don't go in, this is fine. If you are seeking a pro application with any hardwood or commercial metal studs, upgrade.