This is fair; I do find copy/paste to be a bit more difficult with just a finger. If I have a lot of copy/paste, I'll use a hardware keyboard though, which largely negates the issue for me.
Even before switching to using an iPad I seldom had many windows open on screen. Typically an SSH client or code editor and one or two others (email or other messaging, and a browser). I've found this to be an effective way to work for close to a decade now.
On the other hand, if I'm being paid to work on a project and specific tools are provided, I'll use them. (Though I won't use a mouse if at all possible. Trackpads or an ergonomic trackball, yes, but I find mice to be painful.)
In my case though, I find the iPad to be liberating. I can work from literally anywhere. Case in point: yesterday I was out for a walk when I received a bug report on one of my projects. The issue was minor so I paused for a minute, took out my iPad, and quickly wrote and deployed a fix. If I was using a laptop I'd have needed to find a place to sit and setup tethering to my phone (or hope I was near an open wifi network). If I had to use a desktop, I'd have needed to go back to the office before resolving the issue.