For those of you familiar with Opera, the main changes since 7.54u2 are mainly security (anti-phishing) and interface enhancements. Also, if you ever had problems with Gmail, no more. See the changelog.
For those of you unfamiliar with Opera, Opera is a secure, fast, and highly functional browser. Think Firefox, but without having to download eight thousand extensions for a clean, fast experience (e.g. mouse gestures), and better realizations of many features (e.g. tabbed browsing). Well, plus a mail client, news reader, IRC client... Of course you'll need to download a whopping 3.59 MB file, for Windows anyway; I'm not sure how big the Mac, Linux, Solaris, FreeBSD, OS/2, or QNX installers are.