Opera has been my default browser for a long time, but the pre-release versions have lately all been very poorly integrated into the system and I am becoming frustrated to the breaking point. The browser is fast, reliable, full of features, and offers an unparalleled ability to customize the browsing experience. My frustration is with the development versions for Mac do not open web locations from other applications unless Opera is already launched. The best it will do if it's not open is launch and open the default page instead of the URL it's supposed to open. In some applications it returns the URL (somehow or another) back to the application - email client or news reader, for example - and causes that application to attempt to open it however it interprets the system message. This is supremely frustrating and just stupid, in my opinion. Opera needs to address this poorly planned development approach and eliminate this frustrating behavior. In the past couple versions, this was not correctly implemented until the actual release and that is way too late! This rating is based on the level of frustration this current pre-release version causes. While I expect this to be corrected in the final release, I can't KNOW that. When (if) it is corrected, I will consider this a five star app, but it's not even close with this major failing.