The release of Opera 9 Preview 2 marks the start of a new tradition: The Weekly Builds. Every week until the final version of Opera 9 is ready, we intend to ship a weekly updated version of Opera 9 on this blog.
The goal is to further open up our development process to our devoted users and allow you to be more involved at an earlier stage than when we ship the next public beta.
The Weekly Builds are snapshots, they are not as thoroughly tested as a Technology Preview or a Public Beta. You should only use these builds if you are not afraid of losing data (e-mail, bookmarks, anything) or crashing your computer.
I think this is a good move on Opera's part - the popularity of the Firefox nightly builds allowed Mozilla to have a continual stream of bug reports and helped increase the overall quality of the final released product.
Whilst Opera is not open source, the frequent builds will keep the community involved much more. Of course, bug hunters won't be able to propose patches, but very few Firefox testers do so anyway.