I use Windows 8.1 and the lastest version of Opera and Bitdefender Internetsecurity 2015. After installing Opera 26 I have to wait nearly 1 ninute and more, before the new (or the old) startpage starts.Also surfing was very very slow. First I tried changing various options in Opera, but then I looked into Bitdefender ...and there I found the problem. If there is the active virus Control button on, Opera is extremly slow. After stopping active virus control opera runs fine.
So I´ll write the problem also to bitdefender.