In just one simple change, the Gmail interface has gone from being hands down the best email client in existence to one that makes me rapidly enumerate my alternatives.
At one point, Gmail was a marvel. It was the first time I'd seen such an interface not just work in a browser, but feel as natural as any native email client. Gmail overcame perceived technical limitations and provided a really slick UI that a lot of people really loved. That's two major successes there. I don't think I'm exaggerating when I say Gmail put the browser on the map as a way to build serious and fluid applications.
So it's a shame they've decided to cripple the interface by making it seem like writing email, while they grudgingly support it, is not something you're actually supposed to do. It's not even a technical problem: they've just woken up one day and decided that their users are wrong.
This is one in a series of examples of Google pushing out horrible, user-unfriendly interfaces. Google Groups, Analytics, AdSense, and Webmaster tools all fail to delegate GUI behaviour to the browser, and instead force the user into a weird little user interface domain controlled entirely the site. Getting any useful information out of these sites can be hard, because they tend to react strangely and unpredictably to things like trying to open links in a new tabs.
Google has always asserted that its employees are exceptional, and indeed, in that an increasing number of them appear to have never used the web before, they are.
This is a serious question: does the person who designed the new Compose feature actually use email?