What I'm really wanting is the ability to have completely separate IMAP accounts for my various domains, but it's good to see they're adding calendaring, that seemed like an odd omission
I know they've been working on it for a while, I remember reading at least one progress report or the like.
They undoubtedly got diverted by being bought by Opera when they sold the company to it in 2010 and did various things for it, then bought the company back in September of last year. Now that they're again their own masters, we've been seeing a lot of improvements ... and I myself am happy that I can continue using their older "classic" UI because I don't think their New and Improved one is, at least for myself and how I use it.