"Twitter already said that most people access Twitter through their web ui and mobile apps."
My problem with this stance is the same problem I have with so called "browser share".
I am not beholden to a single interface. I'm human. I'm dynamic. I move and change.
That means sometimes I use the website. Sometimes I use the mobile app. Sometimes I embed Tweets on a website. Sometimes I use a website's embedded tweets to follow them instead of following them on Twitter. I send photos and tweets from apps, and I consume tweets from multiple sources.
Twitter is almost as ubiquitous as water for me, the ways I consume and use it in my day to day. There is no single one size fits all interface to Twitter in my workflow, only Twitter the service. Because if there were, if I had to go to the website and only the website, or the app and only the app, I wouldn't use it. I don't use things that get in my way. You either fit into my workflow, or you don't.
And I'll miss the Mac OS desktop client if the rumors are true, because the website doesn't have a simple way to switch between multiple Twitter identities if I'm running a personal Twitter, a brand Twitter. And also because they bought Tweetie only to, eventually, kill it. But we've had this discussion before.