As this Opera 8.5 review took awhile to put together, I might as well post it here as well. I’ve been an Opera user since v6 after being fed up with reinstalling Mozilla and its extensions. Firefox has a lot going for it these days, but it still doesn’t feel as nimble as Opera to me, and the default install still doesn’t cut it feature-wise, so I always have to go dig for extensions that invariably muck the install up. To be fair, there’s plenty about Opera that could annoy/confuse some users so I try to cover both sides.

Pros

• Undo (ctrl-z) opens closed tabs (since Opera was opened!) with full history. This is the handiest feature.
• Close Opera and restart where you left off with all tabs loaded (or don’t, it’s up to you). If Opera crashes? Just reopen, everything’s there.
• Advanced features power users expect, like mouse gestures and the two above, Just Work out-of-the-box without worrying about extensions. Search the web for how many FF users have had to uninstall, manually scrub their registries and Program Files, reinstall and redownload all their extensions. I suffered through lots of this with every Gecko product before sticking w/ Opera.
• Install new versions over the old ones, or start fresh in a new folder and run em side-by-side. It Just Works.
• Super customizable with the best skinning in the business. 1) click skin (it shows what your browser will look like with all your menus/toolbars instantly) 2) keep it or don’t.
• Dead simple panel usability. It’s just a bookmark in a frame, put anything in there. I have my TaDa list in front of me every time Opera opens.
• Instant print preview with fit-to-page. IE users are used to neither..
• Notes is the perfect web researh tool. Copy page text to a note (it remembers the URL) then add your own text. Double-click the note to return to the page.
• Javascript: Fastest engine on Windows, excellent bookmarklet capabilities, User JS without the vulnerabilities of Greasemonkey, and Opera allows access to it’s JS console so JS authors can get fancier JS errors in a panel.
• Lesser target for evil than FF and IE. Of course, no ActiveX.
• Great download manager that remembers source URLs.
• Helpful forums and users
• Now free and ad-free :)

Cons

• It can’t install advanced 3rd-party extensions that dig into the chrome, etc (though bookmarklets may do the job).
• Non-savvy web users used to IE may be overwhelmed or disable cookies/JS/images/CSS and forget how to re-enable them. If dad is used to clicking "the blue e", FF may save you some tech support calls.
• Some sites needlessly hide features from/block it. Savvy users can usually get around these and Opera handles everything fine, but others might find it very frustrating.
• Older versions lacked full AJAX support (used in Gmail). This fact contributes to the problem above.
• Embedded Quicktime and RealPlayer plug-ins sometimes are a pain to get working, and may still fail if the site used incompatible HTML.
• Opera’s error-correction is a bit different than IE and FF, so sites made by amateurs that "made it work in IE and FF" may render differently.
• Like any highly customizable app, Opera gives you the power to really mess it up (though it can always be fixed).
• Lacks IE/FF’s in-browser rich text editing interface, though these are mostly common in CMS’s.
• Like all non-IE browsers, lacks ability to verify signed executables you open off the web (though signed doesn’t necessarily imply safe).