I've recently been working up my chops on the mandolin. Since the mandolin shares the same string intervals as the violin (G, D, A, E) the transition from violin isn't totally outrageous. However, there are some obvious differences: picking vs. bowing, frets, double strings, etc. I always love trying out different instruments because I find it helps me in my teaching studio. I get to experience exactly what my students experience in terms of trying to train your mind and body to do something totally new. I have to remind myself of the same things I tell many students: "Practice more slowly!" "Start simple!" Chris Thile's mandolin video Essential Techniques for Mandolin has been a big help. It's also such a joy to see my technique improving day by day, even in very small ways. Learning the mando is turning out to be a very rewarding challenge. The most difficult part for me? My left hand fingertips are sore! Turns out violin finger callouses aren't nearly tough enough to withstand mandolin strings. :)