The Ebow is great, I waxed lyrically about it on the old forum, I seem to remember.
I don't know how it works on an acoustic instrument, as I have only used it on an electric guitar.
I think it's actually a very subtle device capable of a great range of tones.
Here's some things that I do with it:
* Always use it on the neck pick-up with the tone rolled right off fully and the volume pot backed off a
* Try it on a clean sound, there are a lot more dynamics available
* Don't just play over the 'hot-spot', you can get an overly 'hot' sound there, experiment with its
position relative to the pick-up
* In my experience, it works equally well on single-coil and humbucking pickups
* Use it cleanly - like a slide you can get a lot extraneous noises when skipping strings
* Don't overdo the reverb - it creates harmonics which can get very loud, I almost always use a compressor with it
Here's a short mp3 of a cello-like sound that I get from the Ebow:http://www.petekelly.eclipse.co.uk/celloebow.mp3