I would assume that the freedom
inverters are at least as good as a $30 autoparts store
inverter. I used the $30 model for years on my NorSea and never found it to fail. It ran several different laptops over the years, charged the toothbrush, charged the batteries for the blender (aka, margarita machine), and also charged my Makita drill.
Virtually everyone I know from the Oakland Yacht Club who went cruising in Mexico in the last few years has installed one of the freedom
inverters. I have never heard a complaint and have heard lots of praise for the product.
I intend to put one on my new boat because its cheaper, and more efficient than the true sine wave models.
The reason I would not plug my computer into the 12 volt system on my boat is because of the rf interference that is usually present on the 12 volt side of a boats electrical system and because the computer would be one more thing to put at risk if someone switches off the batteries while the alternator is running.