Search The Firing Line for the history on it. A PNW defense contractor with a huge 300+ security force returned every one of their Sigma's a couple years ago. Never heard of that happening to any other gun.
No doubt the Sigma has been responsible for more controversy than any other firearm. The earlier ones did have problems, hence the bad reputation. The ergonomics of the Sigma is better than the Glock, in my opinion, and other than that they are almost identical in mechanics. Most people who bad mouth the Sigma have never even shot one and just repeat stories they heard from someone else. I have owned three Glocks and traded off every one of them. Besides, in this day and age I would rather buy an American made product. Here is a link for the Sigma parts layout...
http://www.again.net/~steve/ipb-sandw-sigma.html
Here is a link for the Glock parts layout for comparison:
http://www.topglock.com/info/partgraphic.htm