When creating a circle with a very small radius of 0.01 (m), Leaflet 0.8-dev renders it incorrectly. I tracked this down to the calculation of lngR in L.Circle._project an patched my version to use the old version of this calculation. I have not had a chance to debug the new calculation.

Here is the line and my patch to the old code:

                        lat2 = map.unproject(p).lat;
            //var lngR = latR / Math.cos(Math.PI / 180 * lat); //old way
            lngR = Math.acos((Math.cos(latR * d) - Math.sin(lat * d) * Math.sin(lat2 * d)) /
                    (Math.cos(lat * d) * Math.cos(lat2 * d))) / d;

And here is what it renders like in 0.8-dev:

I am doing testing of hi-precision GPS devices and this is how I test for 'cm' accuracy, so use these tiny radius circles to test results.