Screenshots

There is plenty of sites that host GNU/Linux screenshots out there. Amazingly enought many gnome and kde themes try to mimic MacOS look and feel (and to everybody who knows the mac, it's clear that they fail -- not that they aren't good looking anyway).

Mac users do not change MacOS theme so much. In fact they are not used to, they need an external piece of software (and it costs).
I used to change GNOME themes quite often and so I bought ShapeShifter. There are loads of nice themes (however, they are not as many as gnome ones).
In fact now I do use it only occasionally, and probably I would not buy it again (from Unsanity I prefer WindowShadeX or FruitMenu). In fact I do think Aqua is just more beautifull (but I miss platinum very much).

Here you can find some screenshots.