People looking for a imac are not going to cross shop a Mini. One is a all in one and one is a stand alone desktop.
I'm probably an exception, but I certainly plan to buy a mini after seeing the recently redesigned iMac. In fact, I waited, like many, for the 2012 iMac to be released all last year. When it finally was, I was not impressed with the lack of accessibility, no OD, no user-upgradeable RAM on the 21.5", dumb SD slot location, etc. So I bought a used 2010 model instead, which I modded myself, and am quite content for now.
I expect to use this machine for another 2 years at least; it's still quite zippy with an SSD installed. But at some point I won't be able to run the most recent OS X version (as happened to the computer I replaced: an early 2006 MBP 17" that could only run 10.6.8), and I expect that over time this machine will generally slow down as software grows more complex.
However (and getting to my point), I doubt I'll be buying another iMac. While I like the simplicity of an AIO, I most certainly do not like Apple's design direction of less user accessibility. I like to be able to mod my machines, mainly to get a little extra life out of them (got an extra 2 years out of that old MBP because of an SSD and RAM upgrade).
Therefore, the Mini is suddenly a solid candidate for purchase. Assuming, of course, that Apple continues to maintain the ability to take it apart easily like it has until now. My needs are probably pretty typical for most consumers: lots of web surfing, music storage and playback (I get movies from Netflix through an Apple TV, so I don't have any stored in memory), and personal documents like financial records. I don't need a Mac Pro for that, and in a couple years, a Mini with Intel's latest integrated graphics will work just fine. Heck, the current Mini is plenty capable for my needs (I went with an iMac because I wanted an OD and didn't want to have to purchase a new monitor). My hope is that in 2 years or so, 4K monitors will be the norm, or at least in the process of taking over the market. Fortunately, we're seeing large screen 4K TV offerings pop up as well as yesterday's announcement of Samsung's new QHD laptop. Sharp is getting in the game too. But until 4K screens become the norm, there's nothing for me to get too excited about in computerdom.