It's base off of Opera Classic
Now that's a mean thing to say.
It looks like the idea is to recreate a lot of its UI aspects, but it's WebKit under the hood, as there aren't many real options for that. I was a huge fan of Opera 12, but that was just as much about Presto as it was about the UI.
How recent are these Firefox issues you speak of? As only a light user of addons, I'm pretty happy with their technical direction of late, and subjectively I think performance is on a clear upward trend at the moment.
My biggest concern with the browser landscape at the moment is WebKit/Blink's dominance (especially in mobile). It's nothing like the bad old days of the IE-only internet, but on mobile sites that effect is definitely showing up again, and I find it worrying. My small part in keeping that from getting worse is to not let my own use show up as WebKit/Blink in stats (and to ramble about it when appropriate
I wish Otter luck, though. More browser options of any technical independence level are definitely welcome.