First of all great work on Elementary. One thing that doesn't help with the "Copy of OSX" comments is the video on the front page where the desktop uses the Mountain Lion wallpaper.
It's not exactly the same as far as I know. You can use another picture of the same Galaxy without it being the same picture. Plus it appears for 5 seconds on the video and not all the time. They are other wallpapers shown in the video.
The fact that it needs defending is kind of the point. It looks similar enough to evoke the reaction from most people that it is similar to OS X, which is more than like a goal and not an accident. It may not be the exact image, but it doesn't have to be.
