I like the light, plastic lenses so much more than the old, heavy metal ones. The plastic ones just seem so much tougher and don't get scratched and scuffed up and the lighter weight is great. For my type of travel light weight is important too!
When it comes to plastic there are many types and qualities, but I am reminded that they are also used for motorcycle helmets, military helmets, football helmets, tennis rackets, skis, etc. instead of metal. Also, most military and hunting rifles now have plastic stocks.
Many years ago the thought of plastic camera bodies and plastic lens tubes seemed to not be such a good idea to me either, but since 1988 or so my opinion has gradually changed. These days I more or less prefer it. My new 60D has a plastic shell over a metal frame, but it is nothing like the 550D or A100 (and other low to mid range Sony bodies that I have held). It is really well done and if you don't know it is plastic you might think it is magnesium. I had a magnesium 30D before and still have my A700. The 60D looks and feels good. I take care of my stuff too so don't drop gear but, of course, none of us knows when an accident will happen.
The only camera I have ever had that had visible, but slight, damage was my Minolta XK bought in 1976. It was a heavy, metal camera. I had not used it much, but one time I dropped it about 2 feet onto a carpeted floor and it landed on the big finder. I don't know how it happened, but it got a small dent in it. It still worked, but it made me feel a bit sick for a few minutes. :) Over the next few years one corner got some brassing where the black enamel had worn off. I sold it on ebay in 2000 to a collector in Japan along with the box, manuals, everything. I took several close-up photos of the camera also showing the 2 places where it was slightly damaged so anyone bidding on it would know exactly what the condition was. My 7000i, 7xi, and 707si are still in good shape with just the shiny plastic a bit dull from rubbing on clothing and also just age. The 60D does not have shiny plastic.
In normal use occasionally the camera or lens might get small bumps on the edge of a table, chair, railing, corner of a building, etc.. Enough to sometimes dent, scratch, or scuff a metal lens, but I have never had any cosmetic damage to a plastic lens or body. The lighter weight is also very welcome to me.