I use an original Jordan Electronics BossTone. I haven't ever used it to re-create a violin, but I will say this: Bobbe is absolutely correct that it takes practice to be able to achieve optimal benefit from it. I use it primarily to create a square-wave or "fuzz" effect for rock-music.
The BossTone has two controls: effect level and gain. The gain is just that. I rarely set the gain higher than the dry output signal. The effect level is another issue, altogether. It's sensitive to string attack as well as to the strength of charge left in it's battery. A desired setting with a new battery will not be the same as the battery weakens. Also, if you open up the effect level to maximum, as Bobbe indicates in his YouTube tutorial, it becomes a very tricky device to use. The BossTone is ultra sensitive to it's incoming signal. If you set the effect at it's highest level and you're not familiar with it (read that well-practiced), a lot of high frequency harmonics and "bee-in-your-bonnet" sounds will emanate from it. Bobbe's demonstration employs single string picking. However, other (non-violin) effects can be achieved with 2-string picking. Usually the I and the V intervals. NOTE: If you pick more than two strings or it you if you pick the III and V or I and III intervals it will tend to sound like a train-wreck. Also, your picking and blocking techniques will need to be very precise, as the BossTone is sensitive to these, too.
For my needs, I set the effect just beyond the transition from dry signal. At that setting I get something akin to (I didn't say identical to) an overdriven tube amp sound. As the battery weakens this threshold will take on slightly different characteristics and adjustments have to be made.
As I said before, picking attack is a big part of how good or bad the BossTone can sound. Botton line: If you're looking for state-of-the-art effects, this ain't it. But if you want a decent low-tech effect for achieving tube-overdrive or "string" effects, and are willing to spend time adjusting and playing through it, the BossTone will get the job done. Without practice it WILL sound just as awful as b0b and Bobbe have said.
Oh, one other thing: The Jordan Electronics BossTone has micro-minimal to no effect on guitar tone in-line and switched off. I don't know how subsequent versions compare as I've never used one of them.
Hope this helps.
Keep on pickin'!
Glenn
Get the video and listen. 
