Last week I got the mid-range off-the-shelf mini at MicroCenter for $599 (yay!). It's the 2.5 i5, 8GB RAM, 1TB HDD.
It's replaced my great old 2008 24" iMac that's still functioning well - but can't keep up with my hobbies that include using Photoshop and Lightroom.
The good news: I love the mini's form factor, the USB 3 and Thunderbolt ports, the SD card slot, and how nicely it plays with my 22" HD monitor that's been sitting around unused since I used it with an old Win 7 laptop for some work-related things in 2010. And just generally that the mini's technology is 7 years advanced from my old iMac's.
The bad news: how sluggishly the mini handled Lightroom and Photoshop. Especially LR. I've been spoiled by the frisky performance of a computer with an SSD inside: my 2013 11" MacBook Air, 1.4 i5, 4GB RAM, 256GB SSD. By comparison to the MBA, the new mini didn't do much better with my photo editing than my old iMac. Although the MBA's CPU and RAM look "inferior" to the mini's, it left the mini in the dust. To open LR, the mini took 45 seconds, and the MBA took 7.
My solution: I dropped the mini off at a local Mac repair shop (with Apple certified techs), to have the HDD replaced with a 1TB SSD. The total cost of mini with the new SSD + the original purchase price will be about $1170 (+ tax). I'm fine with that. I'm fine assuming the risk of voiding the warranty and all that yada yada. No way could I live with a teensy 256GB SSD on my main desktop computer, and although I'm sure the Fusion Drive is a good thing, I'd rather just go full steam ahead with a 1TB SSD. (The cost-comparable options available from Apple are either the 256GB SSD or the 1TB FD.) Getting the mini at the $100 discount to start, and knowing I'll be able to realize a little cash for the old iMac, makes me happy with this choice and its bottom line costs. In the meantime I'm using the MBA in clamshell mode. It's OK and I might have just been able to replace the iMac with this setup. But it would require too much use of external drives - my photos alone are about 500GB - and I really like having the MBA just for portability, without a lot of my sensitive personal documents, etc., on it.
I'm hoping that when I bring my newly-SSD'd mini home from the shop, it will handle Lightroom, Photoshop, and everything else a lot faster than it did with the HDD. If it doesn't, you'll probably be able to hear my howls of disappointment from coast to coast!!