I believe the OP indicated that he has a nice desktop, so an iPad + desktop is a great combo for many people. This is my setup, and it works for me.
I agree that the iPad has certain limitations, but with each successive iteration of the OS, these have become fewer. Also, the iPad has some advantages, such as size, weight, and long battery life. For many folks, it is more than sufficient as a mobile replacement for their laptop ( especially if they have a desktop to supplement for heavy lifting).
While I do larger scale content creation on my desktop, I can create short documents with relative ease on the iPad. Also, the iPad is great for reviewing and annotating PDFs. The device can be very productive and useful even if it isn't my go-to computer for large content creation.
This Christmas, I was planning on replacing the family macbook. Then, I realized it hadn't left the dock since I bought my first iPad almost 3 years ago. So instead, I bought a Mac Mini for the family, iPad for wife, and iPhone for my son......essentially for the same price as a base level 13 inch Macbook. Of course, I already had a monitor, keyboard, and mouse, since the older laptop had been docked. This won't work for everyone, but it was a great option for our family.