Charged cordless drill, cell phone, old laptop and a bunch of AA/AAA (those through their own AA/AAA charger), all with $20 MSW inverter by GoPower. Never a problem.
Which doesn't mean that you can't do some damage with MSW. Marc is probably right that transformers, motors and other inductive loads don't like MSW AC current. My AC shaver sounded louder and "shrillier" on MSW inverter. So it's better to use PSW, this would cost 5 or 10 times more than MSW. Since none of these items was too expensive, I didn't care.
Yes, there are DC-DC converters like that Ryobi in the post above, but it's easier to run an inverter and use OEM AC-DC chargers and "wall warts" than to find a proper DC-DC converter for each of your devices. Not to mention that you only have one cig lighter receptacle (in fact, my trailer has none).