Don't buy Sketchup 2013.
Trimble, if you're reading this, shame on you. I paid $560 for 2013 Pro. Crashy on my iMac, on my Air, and on my Windows PC (in the "Make" form).
Sketchup was (was) a wonderful 3D CAD program that anybody could
use. It was free. I've done amazing things with it at LRRD; it's
History here. Promoted by Google, then sold to Trimble.
If you're running version 8, keep it.
Trimble has broken "2013" with licensing.
The support I paid for is a joke.
I know Trimble, I buy survey-grade GPS stuff from them. Sent them $2,500 for a software update last year so I could keep using a GPS unit. Just keep using it, not improve it. Just make it functional.
I hope somebody kills me if: "Your Emriver Em2 is has stopped working? Send us $2,500 and it will start working again. For a while. Sort of"
Trimble might surpass AutoDesk, even Microsoft, at putting a needle in your arm and extracting money.
Shame on you, Trimble, fix this problem.
What I do with Sketchup, or used to when it was reliable: