Heater accuracy (Won Brothers)?

I recently purchased a Won Brothers Pro Heat II aquarium digital aquarium
heater for my 75 gallon. The old heater was too small and I plan to go with
an auto water changer in the near future, which will only make matters
worse.

The box makes claims of +/- 1°F accuracy, which if you read carefully,
refers to the digital readout, not the actual heater. The heater has a
range of 68°F to 93°F. I currently have it set at 68°F, but the tank is
reading 72.3°F on my thermometer and 71°F on the heater LED. I thought 4°F
of error was rather crappy given the +/- 1°F claims and the fact that I
wanted to keep the tank around 70°F. I contacted the manufacturer about the
large error, but they did not bother to respond.

Has anyone else had negative experiences with this product? It will be a
PITA to return it, as it has to go back across the boarder. So I don't want
to go through the hassle, if I can expect another lemon.