Su has wonderful interface, none can beat it's simplicity. It's a good tool for preliminary sketches of more complicated models too and since it exports nicely to familiar formats, perfect for our purposes. I'm trying to learn Blender now, there are limitations in SU, for ex UV mapping is a bitch and poor normal controls (there is a way of defining normals but is extremely rickety chain of operations where one false move can ruin everything... So at some point there is a need for heavier application. For tracks i haven't yet met an object i couldn't realize in SU... Sorry for off topic...
EDIT: Forgot to add one important piece of info for SU/BTB users: do NOT use the inbuilt textures!! Sketchup uses quite expensive style when painting stuff, it tends to create a new material each time you use different paint parameters. You will not see anything wrong, all blacks triangles are the same black but in actuality, you can get a new texture and each time you click paint! You'll end up with hundreds of materials if you're not careful.
What i do: i have a simple collection of basic colors 32x32px PNG that i use when sketching (32x32 is the minimum image size, BTW). Later you can replace them with the real ones. Also at some point you need to paint every single material again using Shift modifier. SU has a tendency to create new materials when you do changes in the UV mapping (how you position the texture..), painting every face that has the current material again fixes that. The worst thing is that those copies are not in the right dimensions so you'll get unexplained crashes later...
How to make sure you don't got conflicting copies of materials: When you export with SU6 you get a face count and material counts (why did they remove that info screen in the more recent versionsi can't understand..), if the material count is larger than what the amount of materials used (the SU exports one or two additional materials that you can delete in XPacker, FrontColor and FrontgroundColor, they are useless trash...) then you have a problem... Check them in the XPacker too. If you got duplicates you got two options. Either merge them in XPacker (if they are identical files, not when they are SU created copies, they are cropped and scaled, sometimes rotated, easy to see the difference) or do a new export. Before you export, paint every material again using Shift to make all faces that uses that texture to use the exactly the same source and at the same time, one single material. We need to restrict our material counts heavily in our projects anyway so no room for duplicates.
If XPacker complains when you are deleting FrontColor and/or Foreground color, you can merge either of them to any material used in the project. Those textures are not suppose to be in the model. FrontColor (and BackColor) are the texture SU uses as default when creating new faces. ForegroundColor is something similar, it never shows itself in BTB or ingame, it's unused in the final model.
The A.I. cars anyway. I haven't tried driving over them myself yet...
