IntelliJ is my IDE. I'm excited about this because it's in a web application, not because I've never seen code completion before.
That said, I disagree with the larger point the op is making. When you work in a technical field you tend to figure out the tool for a task, grin and near through a finicky setup process and then dismissing improvements that reduce that friction as trivial/unimportant, even though those improvements mean its able to solve the problem for an exponentially larger market.
A classic example is rsync and dropbox. It's less pronounced here, but the more advanced web code editors get, the longer someone interested in the topic can mess around and try things out without setting up a local dev environment (multiple hours of totally unfun work if you're a novice), the more likely they are to stay interested and push through and get over that hump when the time comes.
[1]The video(100% worth watching) http://www.youtube.com/watch?v=yJDv-zdhzMY Wikipedia: http://en.m.wikipedia.org/wiki/The_Mother_of_All_Demos
The core functionality was, and still is, quite limited. In some cases it's still inferior to what those early office suites offered.
The ability to access and share documents over a network is nothing new. We did it all the time back then. There was even software back then that enabled collaborative editing of documents, in real-time.
For all the hype we hear about how great JavaScript is as a programming language, and how great web apps are, we just don't see that translating to improved software.
When these web apps don't offer anything beyond what we had with desktop software decades ago (and in many cases are even worse), it's hard to get excited about them, and it's impossible to consider them to be "amazing".
c9.io codenvy.com nitrous.io