fiddlers often use fine tuners b/c they use steel core strings which do not stretchg as much as perlon or gut, therefore are much more sensitive to tuners. that is also why classical players use them on their e strings (the e is always metal).

the biggest drawback may be that adding fine tuners to a solid tailpiece changes the ratio of the string. fiddles are made to have a specific ratio of string distances from tailpiece to bridge and from bridge to nut, and the add-on tuners change this ratio. i have heard of some people using viola tailpieces to fix this, or using tailpieces with built-in fine tuners.

steve