Just activated my cellular mini the other day. Its a really nice piece, and I'm liking the size. We have 3's as well both wifi.
I got this one for use on location, to run capture one, hold portfolio photos and for web access when I don't have wifi and I need more screen than the iphone 5 provides. I only have 1gb of data for the mini so I'll use it sparingly.
I was not sure about the size but I really like it, its very comfortable in the hand and its quite easy to read. It fits easily into my Lightwares camera case or my wife's purse ( a good option since we work together).