Pwn2Own
Reports like this are great if you're bored and want to stir things up around the office, but my favorite place to look for info about which browsers are the best/worst is the Pwn2Own competition at CanSecWest. Historically Chrome was the most secure with its sandbox architecture, but this year the compeition was won with two 0-day exploits, one for Chrome and one for IE, with second place going to a 0-day exploit for FF. One thing is for certain - no browser is really very safe and represents the best potential attack vector for exploiting a system.
I also notice that this report is labeled "Part 1." I wonder when Part 2+ will be released?