I just took a look at one at Best Buy, and compared it to a Mini. The 2013 Nexus 7 was palpably faster than the iPad Mini they had in the store on loading pages and switching apps, which is not something I could say for the 2012 Nexus 7 or any of the other 7" Android tablets out there right now (I've repeatedly done side by sides with the Nook HD, Asus Memo, Galaxy Tab 2, etc - owned a Nook HD briefly).
I can imagine Apple doing a modest upgrade to an A6 and a 1280x960 screen (maintaining the 4:3 aspect) and being competitive again, the A6 is much faster than the A5 in the Mini.
But right now, on the hardware front, the Mini isn't competitive unless you just need that extra inch of screen for some reason. So for the first time I'll say - if you're buying an iPad Mini, you're buying the ecosystem and the name, not the hardware.
I was sold on the Nexus 7. I'm going to wait for the 4G version, supposedly ~$350 with 32GB and will work on most carriers including AT&T and Verizon (I'm coming from an iPad 2 64GB/3G Verizon only).