I would like the vertical tabs in only one window for just that one set of tabs. The other windows would stay horizontal as usual. It is currently not possible.
I think I will only use this feature if I cannot determine what is in a tab by mousing over it.
The only problem I have with opera is opera playing videos when it starts up and I cannot find them. I have found a way to locate them but it still a chore. FYI: I usually have about 10+ opera windows open with about 8 - 60 tabs each