I have a Bosch oscillating tool that I like a lot, but it's cordless, and only runs for about 8 minutes before you need to change batteries. I ended up picking up a cheap Harbor Freight corded model out of frustration, because I was using it for all kinds of detail work around the site.
They are one of the safest kinds of saws to use, but you need to be careful about repetitive stress injury (RSI). If you have carpal tunnel, the vibration of the saw can cause a flare up. There is also hand-arm vibration syndrome (HAVS) also known as 'vibration white finger'. A long day of using the oscillating tool generally meant a long night of feeling like my hands were asleep. Stretches helped, but the real key was learning how to hold the saw: loosely. Let the weight of the tool do the work, and keep a very loose grip so that the vibration is only slightly transmitted to your hands and arms.