Make sure you check to see if the foam insert behind the black plastic cover has been removed. It retains water and encourages corrosion. Its only apparent use is to dampen noise, although taking it out makes no difference. The 08 onwards models don't have this fitted anyway. I took mine out when the bike was 6 months old. 18 months on there is just a bit of corrosion and nowhere near bad enough to be visible past the cover. I've now soaked the area in ACF50.
<a href="http://www.flickr.com/photos/davedyer/3428832511/" title="10/04/2009 by Dave Dyer, on Flickr"><img src="http://farm4.static.flickr.com/3617/3428832511_03f130d917_b.jpg" width="768" height="1024" alt="10/04/2009" /></a>
You can see the water stains where the water enters the top of the cover and runs down. Obviously on wet salted roads this is very corrosive where the alloy is unpainted, the rectangular squares either side of the small square black cover Again, from 08 onwards the front engine cover is completely painted.
<a href="http://www.flickr.com/photos/davedyer/3428830539/" title="10/04/2009 by Dave Dyer, on Flickr"><img src="http://farm4.static.flickr.com/3559/3428830539_9ea578bd54_b.jpg" width="768" height="1024" alt="10/04/2009" /></a>