High speeds for retraction can cause the metal filament to clog. Burrs are easy to clean off with your finger or hobby knife. Try to clean as much as you can. Tumbling will smooth out the surface but any larger bumps will only get smoothed out into a blob.
Parts are heavy compared to PLA prints. The bust pictured above measures 72mm tall x 85mm wide and weighs 80 grams. The same print in PLA weights only 12 grams! Both have 2 shells and 10% infill.
copperFill has enough flexablity to withstand extreme bends. Applying force will deform the model. When parts break, they slowly tear before snapping.