An interesting review which sings the praises of the new VivoBarefoot EVO II. Mine are currently being shipped to me, and after reading this review I looking forward to seeing how they feel.
I would be hard-pressed to recommend any significant improvements to this shoe. I think Terra Plana has improved the basic design of the shoe to the point where improvement is unnecessary. I would like to see specific models designed for specific conditions. For example, a lighter model with a thinner sole would be ideal for short road races. Another model with more aggressive tread would be good for muddy conditions.
http://barefootrunninguniversity.com/2010/10/29/terra-plana-vivobarefoot-evo-ii-review/