There are 3 problems with CoronaRoundEdge map:
1) - Intersecting objects no longer blend together. This used to work in older versions. (I have not used corona for some time)
2) - No options (radio buttons) anymore for excluding/including geometry for blending (Originally these were available)
3) - Result has dark shading problems. MODO round edge render works better. (This is also not geometry based so Corona should be able to achieve the same result).
Corona 1.7 RC3Older Version of Corona: