checkthegate - Very good scene you've got going there!

Rutra - Nice work as always. I would have gone pretty much with everything you've said here, my basic render settings are almost identical to what you have here.
The one thing which stands out for me which I have come to experiment with on most scenes is the 'quality boost' tab in the light editor. If you turn this down as you have done here & have other settings right to compensate then render times really will come down. I am surprised you got such results with a -4.0 setting though!
BTW, what did you use for your 'softness' setting for the sunlight? I know changing this setting can really enhance some scenes depending on how you want your light/shadow spread, but going too high on this setting will really increase render time.

Top marks again Rutra for helping people out with settings!