I've already ordered one of the dual radio Extremes. I have two of the old ones running now extending my wireless. I can't justify replacing both but I don't need the guest network and 5.8GHz upstairs (as much) anyway.
I am also looking to pick up a Mini at some point in the next month but I can't decide what configuration makes the most sense. The $800 option is overpriced compared to a do-it-yourself job on the $600. The Mini isn't friendly to open, though. I'd really have liked to see a 500GB drive in the more expensive model. The 2GB of RAM should be sufficient for my needs (media server and kids computer) but more RAM is always nice and not terribly expensive. The CPU upgrade seems very pricey at $150. Of course that's not something I'd be doing later myself (unlike a drive or RAM bump). By then I'm up to almost $1000, though, which seems like a lot for the Mini vs. the low-end iMac.