Never used one before but am interested - does it only work on stringed instruments? Can I use it on anything that can resonate, say a metal table leg or piece of wood? Does it feed out of 1/4" jack or something?
I've used an Ebow a bunch in the past for scoring, and in a couple of "experimental music" projects I was part of. I layered a bunch of Ebow tracks for ambiences for a couple of plays (Alice in Wonderland being one I can recall). It actually doesn't take all that long to get electric guitar strings going with one if the batteries are fresh. Acoustic strings are more difficult. I've also used it on an ektara for some other sound design stuff.
There was a period about 4 years ago where I realized I was reaching for the Ebow on just about every project at some point, so I put it away. I've been gradually re-introducing it.
To answer the 1/4" jack question: No, it's a battery-powered device that emits no sound of its own, and you hold it over the guitar string. There are guide grooves in the bottom that sit on the adjacent strings so the Ebow is lined up properly. To play on another string, you move the Ebow so that it's centered on the new string. You can mainly only play one string at a time. Skipping strings to play complex melodies is a little more challenging that just sliding up and down one string, as you can imagine.
My guess is that it doesn't put out enough juice to vibrate a metal table leg or a piece of wood.
Fernandes makes a device called the Sustainer that is the width of a guitar pickup and is designed to "excite" all the strings at once, and that might be more suited to the table-leg experiments. I know a guy who has one but I've never actually heard him use it.
Here's an ambient-ish piece I worked on about seven years ago using an Ebow on a Les Paul for the "frippertronics" guitars. I think there are 2 tracks of Ebow on there.
I too have never used one, but it might be a good exciter for electromagnetic recordings: Like here.
NoiseJockey's using an eBow: http://www.noisejockey.net/blog/2009/07/23/misusing-the-ebow/
I've used one on guitar -- I don't own one, but I've played a handful of sets where I borrowed one. Mixed with delay and wah, you can get some crazy awesome sounds.
I wouldn't doubt that the entro to this video is all ebow, wah, and delay: http://www.youtube.com/watch?v=1qzis05HisE