Hi!, I'm a new one here. First let me tell you, this forum is great, keyboards are like a new obsession to me so I enjoy reading about them a lot.
I've being using opera since I left Netscape (cant recall if firefox existed then) and now I cannot use anything else. In my job I need to use firefox (iceweasel actually) for some things mostly with one of the systems that does not work in opera and firebug. I hate it! is slow and heavy, one of the things I dislike the most it that all those basic features I'm used to come in the way of plugins. Opera comes full of cool features already available and is lighter than others.
An important thing are the key shortcuts, for example, holding shift and using arrows let us navigate the site really fast, and as this a lot more. The M2 mail client is great, very lightweight and simple.
The only disturbing issue imo is flash under linux, there is no plugin for opera so it uses firefox one, but it's very unstable and resource hungry, specially when opening flash sites in several tabs.
Other than that is the perfect browser I can imagine, I would recomend every keylover to give a try.

Cheers!