Mixed emotions here. I think it makes every sense for Opera to do this. The cost of maintaining their own rendering engine must have been huge and the advantages it brought were slender. It's also good to have another major player contributing to webkit. On the other hand it's a step closer to an unhealthy monoculture in rendering engines. It's already the case for the mobile web that people are starting to define st…
I think this is right on for Opera, it has always set itself apart by it's usability and features and I think browsers need to get innovating more on that front.