Firstly, for anyone not already using at least prosumer photo-editing software, the latest iPad apps are preferred to desktop apps by everyone I've seen use them. So lightroom or photoshop users may not be satisfied, but most people looking to make a few standard adjustments are going to get the job done faster and easier by not putting that tablet down.
And for substantial amounts of text entry, sure, the keyboard is great. But you don't need traditional OSX/Windows style keyboard-mouse interfaces to handle a keyboard.
In terms of media consumption I do not miss anything with the tablet but I find myself so often getting up from the couch walking over to my desk to get some simple tasks done in software XY because traditional software still beats most apps.
Having all those software programs running on my tablet will be so amazing!
I disagree. I see no reason why my mom wouldn't want a single computer to use on a couch for browsing, and on a desk with mouse/keyboard for chatting or photo editing. This seems like an obvious convergence of 2 specialized devices. There are trade offs of course, but if they can deliver a good experience, I think users would be willing to trade the computing power of a desktop for a single all-in-one device.
The next obviously step is to have a phone that can replace all 3, with different docks. And once phone CPU gets powerful enough we will definitely see that.