So... I've been doing a render... for now it's 145 hours long which is kinda weird considering 3600 x 2400 without anything hardcore in it, and I'm rendering it on quad core @ 3.2 GHz. And still... I think it will be ready in approximately four days.
Clouds went pretty smooth, terrain too. But the populations (3 of them, perlin and altitude based) take years to render. Very high quality but still - it's strange. Anyway - I'll wait for it's completion as I have like 65% complete so far.
Here's the screenshoot of the render window.
Any "oh's" and "ah's" together with "this sucks" appreciated
EDIT:
Render settings: Q: 0.875; AA-6; GI-2/2; Soft Shadows - 1/10; Supersample Prepass; No GI surface. Atmosphere - 64; Main cumulus - 273 with optimal acceleration.