The short answer is that it depends on the 'quality' of the electricity. Electronics are designed to run on even voltage and a constant frequency of 60Hz. Generators can sometimes have variations in voltage, frequency, and electrical 'noise' (think static). Many household products such as lights, heating elements, and motors are relatively immune to these differences, but electronics rely on these factors being consistent. I would think that if you spend enough, you could get a generator that would deliver clean power, or there might be some kind of regulator/filter available to clean it up.

You could get one of the surge protector/back-up battery set ups to plug your computer and/or the other electronics into - I have one for everyday use, although I unplug everything if a T-storm is in the forecast, since I have had several lightning-fried computers and phones before I got this. It would probably even out the power from the generator, or not let the uneven power get through to the computer, but I don't know for sure. You could ask someone at the tech support for your computer - I would be a little reluctant to ask at the store where you plan to buy it, as they DO have a vested interest in selling you one. You might be as well offf to get one for each piece of equipment, rather than one to protect many pieces - the price, as I recall, ranged from $50 to $150 at Best Buy, depending on the power protected, and the length of battery life, so it depends on your budget.

turnkey, we got a standby generator a couple years ago and heard the same warnings. I do have a usb device connected to the computer because it takes a few seconds for the generator to kick in and the usb covers that lag. When they installed the generator, we tested the computer (the only thing I was really worried about) and it was fine - don't know what the people we bought it from would have advised if there was a problem.

Generally, I think standby generators are miraculous. We've only had 2 or 3 extended outages, but each time the generator has kicked in perfectly. We have much of the (small) house hooked up to it, and it's great to watch TV, play on the computer, go to the bathroom without a candle, and not worry about whether all the food in the fridge is going to spoil.

I guess I'd ask the people you are going to buy it from what would happen if there were problems with the initial test. They do all say that it can happen, but for us it all went smoothly.