A quick word on the different Opera product streams on desktop. All streams are available on Windows, Mac OS X and Linux. Each release runs in parallel and can be installed side-by-side.
Opera is the product recommended for everyone. The quality requirements are tight and the stability is superb. The channel only receives small stability and security updates between the major releases.
A major release happens approximately every six weeks.
Opera beta is what will become our next main release. It contains the features we intend to ship at a quality level resembling what we intend to ship. No new features or significant changes are introduced between the major releases. Release updates happens every week.
The beta stream is what is often referred to, in development terms, as the testing stream.
Opera beta was formerly known as Opera Next.
Opera developer contains our latest changes. It is a nightly snapshot of our active development, delivered more or less as is with minimal quality requirements.
The intention is to showcase what we are working on and be open about upcoming changes to web technologies. It is not intended for daily browsing. It is provided for web developers (as the name suggests) and enthusiasts who are not afraid of some bumps in the road.
The developer stream is what is often referred to, in development terms, as bleeding-edge or the unstable streams. Referring to the risk of suddenly getting cut by an unpolished developing feature.
An Opera developer release happens approximately once or twice per week. (Thus, not recommended for users with limited bandwidth.) There can be fewer developer releases in the week preceding an Opera release.