The iPhone (original and 4S) were both great devices but too small. I could carry them everywhere, but the reading and browsing experience was cramped, by necessity of the small screen.
The iPad (original and Retina) are big, and lovely for reading and browsing, but too big to hold with one hand. This really is an issue for me, the way I sit when I'm reading... it ends up limiting my use of what otherwise would be a fantastic device.
So, the mini seems perfect. Light enough to hold, big enough to get a fantastic reading and browsing experience. I know it will be a little cramped compared to the iPad (well, expect it will be, but the same resolution original iPad was not cramped at all) but that's a fine tradeoff for being able to use it, literally, everywhere.
I like that they decided to start at $329 with 16GB, about perfect pricing for me. We spent over $650 on our retina iPad with LTE, and ended up not using the LTE much at all.
For our startup, which is heavily involved in iOS, and all of us have iOS devices, we will probably buy 2-3 of these minis.
In fact, I think I'm personally, done with the iPad and iPhone... I don't need the phone part (which is why I've mostly bought iPod touches) .... only went with it because the original iPad was not as portable as I'd like.
So, I'm totally stoked that this device is as it was rumored... I see no downsides to it at all.