I recently switched from Chrome to Opera, and I'm enjoying it. I ran into a slight issue earlier, though, and I thought I'd share it. I installed the AdBlock Plus extension for Opera (in addition to the built-in one) and for a while it was working fine. I watch youtube a lot so being able to block ads on that is important to me. At some point randomly, the ads stopped being fully blocked before videos, and, while the ad couldn't play, I'd still have to wait the full duration. I tried disabling AdBlock Plus and keeping the built in one on, but that caused the ad to just fully play normally. After a while, I did the same thing but restarted my browser after I made the change, and now the built-in one works perfectly by itself. It seems like the presence of the independent extension caused the built-in adblock to start doing nothing.

TL;DR: AdBlock Plus extension didn't fully work on YT and caused the built-in adblocker to stop functioning.