I wish Opera would open source their presto engine. I'm guessing that isn't possible due to some licensing issues. Personally I find it unfortunate that all that amazing work will be lost. While I didn't use Opera due to it's proprietary nature, as a browser engine it was competitive for its time.

I'm having the same feeling now about the EdgeHTML engine which is now being fazed out. This engine was a breath of fresh air compared to trident. It was bringing value to the internet space.

Granted, I do realize there are perfectly valid business reasons Opera and Edge switched to chromium.