I've been using Opera as one of my complementary browsers for a number of years.  They have enjoyed a good security track record with a state-of-the-art browser that offers excellent imaging capabilities.  However, one day after the release, a new proof-of-concept vulnerability has surfaced which can trigger a denial of service attack (i.e., this is a minor security risk where the browser might hang for an extraordinary length of time).   Thankfully, this risk is not in-the-wild and most likely an Opera 9.01 will be released in the near future.

Opera 9 - New Denial of Service POC vulnerability
http://www.incidents.org/diary.php?storyid=1436

QUOTE: Well, it didn't take long.  Yesterday, Opera 9 came out, today there is a proof of concept for a long href denial of service exploit.  No word on when a patch will be available