Zagg
The ZAGGkeys Folio with an iPad Mini.
It is in that family of cases that effectively turn your iPad into a touch-sensitive laptop. Open the case and you have instant access to a conventional (if slightly shrunken) computer keyboard that pairs with your iPad via Bluetooth.
There's just enough of an adjustment to be made in typing on a smaller-than-usual keyboard that it bears mentioning here. If you've never used a smaller keyboard, it'll take a few awkward minutes to get the hang of things, but it's only a few minutes.
After that short speed bump, the ZAGGkeys case will become largely indistinguishable from your standard keyboard in terms of function, feel, and writing speed. Because the case keeps it physically attached to your iPad Mini, it may very well end up becoming your primary means of word processing on the go.
Of course, this all only applies if you use your iPad Mini primarily as a word processor. If you're an infrequent writer, this case is not for you, as it only opens so far in order to keep the iPad Mini's display in line with that of a laptop. There's no folding the keyboard behind your iPad to get it out of the way.
Reading and writing are my primary uses for my iPad, and I happen to prefer reading in landscape mode, so my only complaint of substance is the price. The black and white models of the case are a rather head-turning $99 each. If you want purple, it's $79.
If you're an unstoppable writer who isn't turned off by the price tag, then this is the iPad Mini case for you.
If this doesn't describe you, you're better off to keep looking.