I once implemented this and tried it out. Unfortunately, it interfered with vertical scrolling (if you disable auto line wrap) and zooming (two- and three-finger swipes were wrongly detected as pinch-to-zoom). So I didn't add this feature to a released version as a consequence.

Thanks for pointing that out. (The refresh button works too)

I have to admit that I haven't thought of this. I'll see if I can add it in an update.

Did you try to add the user name and password to the url? Like this: http://user:password@example.com/

I don't think it's possible to disable it after it's loaded. You'd have to reload the page or close it in the top right corner. You can either re-open the preview window or re-enter the url to reload the page without loading Firebug.

Yeah, you currently have to scroll the completion list with your finger and tap to select an entry.

I thought a lot about it. The biggest problem is that iPad keyboards generally lack an Esc key. So how would you get out of the list on a keyboard without an Esc key? (like the Apple keyboard dock and the Logitech fold-up keyboard that I own) 

Because of that problem I've decided to make it touch-only until I find a solution.

In theory it's already customizable, but I haven't documented it yet.

Textastic 4.0 is now available on the App Store!