As I mentioned, this goes back to approximately three years ago.

The developer tools console could do:

- completion while typing

- display JavaScript data structures in more visual way

- breakpoints on DOM changes, events and Ajax requests

- profile network, memory and cpu usage

- navigate cookies, indexdb and websql databases

- reformat JavaScript code

- CSS editor

- work as IDE

- debugger API to work together with IDEs like Netbeans

- profile 2D and 3D performance

Basically, even though I prefer native to web, while using Chrome Developer Tools I had the feeling I was kind of back to Smalltalk.

Additionally their website was better than MDN in terms of information, specially thanks to the many sessions on Google conferences.

https://developer.chrome.com/devtools

That said, maybe Firefox is now on par.

It's there.

> - display JavaScript data structures in more visual way

Sort of? Is the existence of the 'inspect' function enough?

> - breakpoints on DOM changes, events and Ajax requests

I'm not sure about this. I mean, you can set the breakpoints in code per usual but I expect you mean setting them on the nodes themselves and perhaps global breakpoints in the net panel?

> - profile network, memory and cpu usage

This sort of profiling?

https://developer.mozilla.org/en-US/docs/Tools/Performance

https://developer.mozilla.org/en-US/docs/Tools/Network_Monit...

> - navigate cookies, indexdb and websql databases

https://developer.mozilla.org/en-US/docs/Tools/Storage_Inspe...

By the by, WebSQL isn't part of any standardization track and will not be implemented in Firefox as it stands, and neither will IE it looks like.

> - reformat JavaScript code

You mean "prettify source"? If so, yes.

> - CSS editor

There's the Style Editor, and the side pane of the Inspector.

https://developer.mozilla.org/en-US/docs/Tools/Style_Editor

https://developer.mozilla.org/en-US/docs/Tools/Page_Inspecto...

> - work as IDE

I guess the Scratchpad is the closest thing to that. So technically, no. As a side note, there is the WebIDE for Firefox OS development.

https://developer.mozilla.org/en/docs/Tools/Scratchpad

https://developer.mozilla.org/en/docs/Tools/WebIDE

> - debugger API to work together with IDEs like Netbeans

It's possible with the remote debugging protocol but the only implementation I know of is the proof of concept that Paul Rouget put together two years ago, although I don't think he released any code.

http://paulrouget.com/e/devtoolsnext/

> - profile 2D and 3D performance

You mean FPS and such? If so see the profiling tools linked previously.