Terragen Skies

Has anyone here used Terragen to create sky images for Blender (Cycles)? I am interested in creating 360 degree sky panoramas, that I can load into the World shader. Has anyone else done this? Can anyone point me to a good tutorial on this subject? Any good Terragen tutorial books? Internet searches have been rather fruitless.

i have only used the old open source terragen

basically make a simple cylindrical ( equalarea) 90n to 90s and -180 to +180 map

if you need it to be a cube map the perl panotools for huggin work well to convert from simple cylindrical to cube and back