Original lens is VERY tough! 100% shatterproof. It's lighter too which helps to balance the lightweight G2 body.
That being said, my G2 has a UCL glass lens and stainless steel bezel, along with a nice LED drop-in. I replaced the plastic lens mainly because I accidentally scratched the hell out of it with a screwdriver one day.
You can't break it, but you can sure scratch it!