Using an iPad for doing web development and programming
Solution 1:
If you're just looking for a straight text editor, Textastic has a lot of nice features.
For full-fledged web development, check out Diet Coda. It has built-in SSH terminal, SFTP, a great text editor, etc.
Solution 2:
I was all ready to call you mad, but this is looking considerably more workable than I'd have thought.
There is an iOS port of Vim, and if that doesn't work well then you can always use one of many terminal emulators to shell into a remote host and run Vim there. I might recommend the latter ahead of the former, actually; it's not clear how you're expected to get files onto the device for editing and then put them back into their testing environment, whereas running Vim directly on the testing host obviates the concern entirely. Multitasking is a concern here, in that if the emulator doesn't get any CPU time then your connection will time out, but judicious use of GNU Screen, and perhaps an emulator such as Prompt which can maintain connections for a while even when backgrounded, should relieve that problem pretty handily.
As for debugging tools, the ones built into Safari only work when your device is tethered to a computer running the desktop version, but Firebug Lite is said to work in iOS Safari and presumably would work just as well in iOS Chrome, and its bookmarklet can be added to the browser's bookmarks bar for easy access. (It doesn't seem to be working right now in any of the three browsers in which I've tried it, including Safari on my iPhone, but I suspect that's a transient issue related to the apparently quite recent release of a new version with major changes.)
Being similarly equipped with an iPad and Bluetooth keyboard, I'd considered trying the same thing you're looking to do, but wrote it off as unworkable. Thanks for giving me the impetus to investigate further and discover that it can very likely be done pretty well after all.
Solution 3:
Mark O'Connor has written a compelling series of articles (starting with this one) about doing web development using an iPad as a thin client to a Linux remote server.
You basically just need an SSH client app for the iPad (there are several: Mark mentions iSSH), and you have access to VIM or whatever other tools you can run on the server.
Solution 4:
I use two apps for coding on my iPad, though I only use them in emergency situations.
The first is iSSH. It lets you log on via SSH to servers. It also does X forwarding, so I can log in to my workstation in the office if need be.
The second is Koder, which is basically a mini IDE for an iPad. It supports FTP, (S)FTP, Dropbox, WebDAV, and local development. Also, it has Firebug built in to it :)
I'm not sure I'd like to use it 100% of the time (Zend Studio on Xubuntu works very well for me) but it is workable.