Really interesting question this one. I am finding my bigger IPad far easier for email yet the mini is so much more portable for meetings. I think you look less like an idiot too with a smaller device. Will definitely use the mini for commuting and for reading, but am unconvinced about whether it is ergonomic enough for content creation. Will I write letters on it? Unlikly. I am wondering whether games will be more fun in the landscape mode. The jury is still put - it's lovely to look at though!
Still exploring that- but I do know that mini will replace full-size iPad for me. Using BT keyboard I used w// iPad 3, will see how much creating I can do this way. Much of my work involves reading, so this is PERFECT. I went from LTE version to wi-if only- so far, BT tether via iPhone works perfectly when I don't have wi-fi connection for Mini (and when I am not also trying to use BT keyboard).
For me, the question of redundancy is with full-size iPad, rather than with iPhone. I am so far using Mini the way I used iPad 3- which complements rather than substitutes for anything I do in iPhone. I will keep only one iPad because two sizes would be redundant for me- and the one I keep will be Mini. The smaller form factor is perfect for me. Mini will go more places than the iPad 3 already did. I often carried iPad3 sans BT keyboard to cut weight. With Mini, I can easily carry both, so paradoxically, may use the Mini even MORE than full-size iPad.
My company bought me a 16gb New iPad. I have been using it for the last 7ish months for work, but also for personal email, video, media, etc. I picked up a 32gb Mini today and I'm planning to use it only for personal stuff. No company email, and I will be clearing all of my personal stuff off the New iPad. I think that the Mini will be awesome for personal use because of its size and weight. For me, it's not the best choice for business.