Using Sketchup as the main modelling tool with Unity

Has anyone here used Sketchup as their main modelling tool for Unity? If so, I am wondering if this went well, or if there were any problems?

I am considering using Sketchup for architectural stuff, interior, buildings etc.

There are some tutorials on the Unity-Sketchup workflow, and it seems to work very well. I know that Sketchup can get slow when you have big scenes, maybe this is a low ram problem? I also know there is a plugin that reduces the polygon count of models, wich will be helpfull if i import models from the 3d warehouse.

Lastly, I am wondering if there is some guide somewhere, of how many polygons a game scene can have in Unity while running on standard hardware?

 

I havent had the time to read up on scene optimazation in Unity, so is likely a noobish question. But let say I design a city in Sketchup, and I use copies of the same buildings, will it be reckonized as a copy of a building in Unity? Or should I Instead just create the buildings in Sketchup, and then make prefabs on them in Unity, and do the layout (placing the prefabs) in Unity?

Also, let say I want to do a change in a sketcup file, but I have already imported the file into Unity and textured it, and dont want to loose the work I've done i Unity, what would in such a case?