As long as the editor doesn't actually have code completion and code folding it's not an IDE. I was very enthusiastic when I first heard about Bespin but after installing the thing locally I saw it's basically just a syntax highlight layer.
I would love to see a true browser-based IDE but Bespin isn't that just yet. I see how it works for a CMS but it won't replace NetBeans or Eclipse very soon.
I don't there is a reason to loose enthusiasm. I've talked with the bespin team and they know they have along way to go. Just because it's not feature complete doesn't mean it sucks.
It seems like they have built a strong base. Some cool projects have adopted it. And it seems like in a year or two it might even have a really strong feature set. So I'm excited even if I don't use it much currently.
At first I have to admit I didn't quite get the point of Bespin, but I've realized its incredible power as I've come to appreciate the web as a viable platform for most applications. I will probably use it when I transition one of my current projects to the web, and look forward to seeing what others do with it. I have only one complaint so far: alt+left/right is used to move by words instead of the more common ctrl+left/right.
The whole point of Skywriter is the underlying totally new architecture: The use of canvas, incredibly fast rendering and unlimited editing file size. No other textarea-based editor can do that. When it comes to editing source code in the browser, there are often 5000 and more Lines. Other editors slow down or can't even handle such many lines.
Idea for it that me and a friend had: often times when new users need help in IRC they paste some code, and make some changes, and repaste etc to show what their issue is. The idea is to write a plugin for editors that, at a click of a button, live streams the content to bespin^Wskywriter and they can just link the "view into the editor" to IRC so people can see the code in a real time way. Then when they're done they can kill the "view".
As soon as IE supports everything Skywriter uses, we'll be happy to support it... Right now, that means Canvas, Web Workers and CSS3 Flexible Box Model. The latter two are not yet supported by IE9, I believe.
They are currently trying to get it to work on the iPad/mobile safari. That could quickly make the iPad a reasonable mobile development environment.