I use Sketchup a lot for architectural work; for both testing and solving three dimensional design problems with architectural details and for presentation of ideas within a project to clients. As many others do on this forum, I use Cheetah3D as my renderer of choice. I think that the pairing is quite complimentary, and my only complaint would be the lack of a direct .skp importer. Within Sketchup, I group constantly. I make components from repetitive elements and use groups to easily modify elements and keep them from sticking together. I place the geometry on different layers which are organized by material. I try to approximate the color of the material within the layer manager, using the color by layer option as I go along. I export the model as an .fbx and then in Cheetah use the smart folder to link to the .fbx. This way, I can go back and edit the sketchup file as I see problems, re-exporting as necessary. The materials get tweaked in Cheetah, and the lighting and cameras get set at this time. I do a series of small test renders, gradually adding more and more complexities as I go. First renders to figure out views and to see any problems with the model, second to check lighting, additional ones as I add HDRI and/or caustics. When I get everything set, I do final renders which can sometimes last a day or more. Sometimes I do a bit of color correction in Photoshop afterwards, but all in all, the output is fantastic.
I think that the combination of Sketchup for architectural modeling and Cheetah for rendering is tremendous, and would recommend it to anyone who is doing similar things.
Randolph