I have one and took it to work to compare it to a $600 calibrated Power Analyzer. For the price I wasnt expecting to much but I was shocked (not literally) that it was DEAD ON. It tracked perfectly with the calibrated meter at about 20 times less the cost.
These are WELL worth the price. I think I saved the cost of the unit several times over already by showing my family how much electricity things use and that they need to shut them off when not in use.