The latency hiding alone makes it worth it; SSH is miserable over links with any lag, mosh feels as responsive as typing locally until you get into hundreds of milliseconds of latency.
The main benefit for me is mobility, though, not the restore from sleep itself. When I started using this setup I was traveling quite a bit, including just locally (living in a downtown area, I'd start on something in the apartment, then decide to go to the coffee shop, or the growler place, and continue working). Not having to reestablish the connection (even using SSH certs that's still some friction) was very pleasant.
The second is when dealing with an unreliable network. Though this is less common these days, when I started with it I had a lot of issues in my apartment thanks to a neighbor with a noisy microwave oven.
I'd prefer a real IDE on a few occasions (work is C# and Java). Trying to do some side projects to relearn or expand my knowledge of them and their libraries was infeasible on the iPad alone.
In the end, my conclusion is that if you don't need an IDE and can use a CLI or git-based workflow, then the iPad is a fine tool for programming and writing in general. I'm not even stymied by the relatively small screen, it's still better than the monitors I grew up with. The fullscreen and split screen modes also work well with my particular manner of maintaining focus on tasks (I use fullscreen/split screen on my MBP almost exclusively as well).
Isn't that the point of mosh?
"Remote terminal application that allows roaming, supports intermittent connectivity, and provides intelligent local echo and line editing of user keystrokes."