have you tried Kerkythea with metropolis light transport render method? ...I've had less noisey solutions in less time with metal matls...of course I have a dual quad core machine.....it is interesting and thought provoking to see others rendering sketchup models with all the same trials and triumphs using unbiased methods too.....just curious if there was a time/quality difference.......looks great though....

the general rule of thumb for architectural perspective rendering for the last 500 years is to keep the verticles absolutly verticle.....expensive parallax lens are used on cameras to achieve this effect...in rendering apps, just simply raise or lower your DOF ctrl....this makes clients nuts...just an FYI from someone with 17 yrs exp with arch viz....