I have been ready to tear my hair out with how sluggish WordPress 3.5.x Admin is (compared to 2.9.2) on a mobile device. Even on an iPhone 5, every scroll, every zoom, there is a 1 second pause. Navigation is torturous. Also, just getting to Comments and New Post take 2 clicks when they used to take 1. When you are trying to post an article in the car or train, or when time is an issue, seconds count and WP's default Admin loves to waste your time, making it impossible to work with any speed.
So... Why don't I just use the WordPress iPhone app? Because all formatted text you Copy and Paste from somewhere else is stripped down to plain text! Sorry, but this is 2013. I don't want my articles to be just plain text with all weblinks and formatting stripped out!
Juiz' CSS3 replacement Admin theme solves these problems. It's responsive, as in, you can instantly add a new post, write a headline, paste Formatted content, hit Submit, and the article is posted in seconds. Not sure how he solved all the speed problems just with CSS media queries, but this makes the WordPress Admin panel 10 times better.