We have an iPad2 and iPad(3) and our family now has (4) iPhone5s. My wife and daughter also have a Kindle DXs for reading books. So, we seem to have enough screens to go around. If Apple would make it easier to "share" devices, then I think we would get an iPad Mini. But at the moment each iOS device is quite personal, with applications, settings and email assigned to a specific individual. I'd like to see iOS and iCloud offer better multi-user sharing. Then we could really take the device that suits that particular need for the day (battery life, screen size, weight). As it stands now, we each have our own phone and then the iPads have mostly my stuff on them and I need to reconfigure it a bit to let my daughters take one for awhile.
Samsung seems to be the biggest promoter of multiple screen sizes. At some point, there will be too many screen sizes and resolutions to support, but from the leaked iPad mini specs, it seems to be a logical in between screen size from a full size iPad to an iPhone retina display. So a 7.85" mini screen priced under an iPad2 and smaller seems to be logical device given the competition (Sammy, Kindle, Nook) and will enable one to share their iBooks and iTunes content between devices on the same ecosystem.
So, yes, I'm in favor it a smaller iPad and we will likely get one, which may displace some use of our Kindles. We just would like to see better multi-user sharing options in iOS to make it easier for multi-device families.