wrap UV around mountains

Hello!
I came across this example on how to unwrap a UV on a sphere in a shader!

http://www.gamedev.net/topic/487369-uv-mapping-a-sphere-in-shader/

float2 normd = normalize(vtx_position.xy);

// texture coordinates
float deg = atan2(normd.y, normd.x);
deg = degrees(deg);

if (deg < 0)
deg += 360;

deg /= 360;

l_newUV.x = deg;
l_newUV.y = vtx_position.z;


This approuch is interesting but comes with several problems.
The texture wraps perfect around if 1. the object is very 'sphery' 2, no concave shapes included.
Otherwise, the texture is horrible distorted.
Does one have an idea on how to improve this code???

Regards! Tom