Interesting point of view. My experience is almost totally the opposite! I bought a Logictech keyboard for my iPad 2 for an overseas journey, because I wanted to travel light, but knew I needed to type a lot.
It transformed my experienced of the iPad!
I now have the keyboard almost permanently fitted to the iPad - it makes it comfortable to use on a couch or in bed because the keyboard can rest on you lap or stomach and you don't have to hold it, like, well, a laptop!
I have personally never found the on-screen keyboard much good. My typing accuracy and speed (normally quite good) is half what I can do on a MacBook, and the virtual keyboard occupies half the screen real-estate.
My experience with the Logitech keyboard was that an iPad could *almost* be used instead of a laptop for basic tasks. It obviously can't run a lot of "serious" productivity software (although this may change over time as vendors offer products for iOS), is underpowered compared to a MacBook (the difference is decreasing), and the screen is still too small.
If Apple do release an iPad plus, it needs to have a good keyboard option. I like the idea of detachable keyboards. Sometime I would like to use the device in tablet only mode (during a commute, standing, in a meeting where a screen can be a "barrier", but the keyboard is absolutely necessary (for me) to be productive.
I will watch this space with interest. Either an iPad 12" + keyboard, or a lighter MBA 12" would fit the bill, but ideally I'd like an iOS / OSX hybrid 2-in-1. An MS Surface "done right".