From what I learned during research on solar power systems (and the heart of the system; the inverter), the sine wave that Theo alludes to is key. True sine wave, the type you get from utility power, is ideal. Modified sine wave is also very good and usually works well with most computers.
(borrowed from the www): The problem with wave form only comes into play when specialized pieces of equipment need to be powered. Here are a few devices which could have problems when they are connected to an inverter producing a modified-sine wave signal: oxygen concentrators, fax machines, laser printers, high voltage cordless tool chargers, equipment with variable speed motors, electric shavers, and garage door openers. Knowing this, make sure you are not shaving while you are on an O2 machine while faxing something from your laser printer while the hired help is using the circular saw to fix the header where the garage door is attached, as he makes sure the door opener now operates.
I don't know if brushless has a direct correlation with the wave form. Tom G would probably know.
