I use a fairly large font because readability is important to me, so I get something like 85 x 60 characters on the screen. Width-wise, that's fine (and I set Vim to wrap long lines anyway). I also would have thought I'd miss that wider overview, but somehow I don't. I've become quite proficient with vim's navigation and movement commands - perhaps that helps a lot. I sometimes code on a 1600x1080 monitor with at least 6 times as many characters on the screen, but I don't notice the difference any more.

Except: when merging changes. Then I really want the screen divided into 4 sections, and the iPad is too small to do that comfortably.

That said, I've noticed a trend in my coding style to prefer conciseness and locality. This may be a subconscious reaction to the smaller viewport I'm using.