Sorry, but imho a cheap Dell would be more comfortable to work on than some weird ipad/bluetooth keyboard/whatnot combo.

And decent only starts on the far other side of that spectrum.

I think it would be interesting to see the amount of productivity people lose using their iPads.

In my experience my iPad means I am using my laptop a lot less, but it's taking me more time to do the same things I did on the laptop on my iPad.

With the advent of ultraportable laptops a few years ago, I've almost entirely stopped using my tablet(s). The upsides of a smartphone's form factor are self-evident, but a suitably light laptop is (IME) so far superior to a tablet in comfort, usability, and efficiency that the category has been practically obsoleted for me.

My current laptop has a 13 inch screen and roughly the dimensions of an 11 inch macbook air. There are very few times I find it less convenient than a 7 inch tablet, and almost none compared to a full-sized tablet.

There may be value in using an iPad as a dev machine simply because it provides a separate environment for only doing dev work. Given that habit (and thereby procrastination) depends greatly on environment, it's possible that using an iPad strictly as a dev machine could increase productivity by subconsciously associating the iPad environment with efficiency. That is, if you're on your iPad, you know you shouldn't be messing around, and you use it only for work. Whereas if you're on your laptop you might be tempted to lapse into time sinks that you already associate with your laptop.

I tried doing some serious writing on an iPad (with external keyboard) a few years back.

The number of times I needed to touch the screen or switch apps made it a pretty inefficient experience.

If I wanted a 'cheap' device to write on again I'd probably try a Chromebook

One is talking about software and the other is talking about hardware form factor.

If the form factor is uncomfortable, sometimes you can't program around a solution.

That's actually all the "GNU" parts of gnu/linux that people mention here and there when being pedantic about linux distributions. No linux involved at all as long as you are on darwin.