Unlike Google I've been windows free for greater than 10 years. It is truely a shame that the backbone of Google (Linux) is supported on it's products. I would really like to use SketchUp but as stated by others my experience with Wine has not been positive although it been a few years since I tried Wine. As far as Linux being a sever OS and not a desktop, it is a great server OS but in case you haven't heard it has made great strides on the desktop (Ubuntu, etc.).
I know this is just spit in the wind but I think Google management should take another look. The message you send is that you use your competition (Microsoft or Apple) to use this product.