I've been playing around with World Machine, but only trial version. I simply had no $$$ for the full one. But I must sadly admit that I didn't bury through WM enough to help anyone... and it was soooo long ago... I was still on Wingdows these times

Seriously, try reading the help, not just having a look at it. I remember that help files for World Machine were pretty well-written and thorough.
And have a look at Terragen. With this you can render the maps from WM in amazing quality (use Classic Terragen, 'cause with 2.0 anyone can get lost, I believe).

Cheers!