Opera 41 delivers "86% faster browsing" but only when using more than 42 tabs open from the previous session. When it's around 10 tabs or so, there's about a 50% speed boost. Besides the startuo improvements, Opera 41 has received optimizations so mobile devices have a longer battery life, hardware-accelerated video pop-out support, and other optimizations. Aside from performance optimizations, Opera 41 also has personalized newsreader improvements.
More details on the Opera 41 web-browser update via the Opera blog.