FWIW, I´ve ordered a Mini; delivery date stated as Dec 12th.... So I´ll know something more a few days later.....
Details: I have a 2007 MacPro w/ 2x2.66 Dual-Core Xeons and 7 GB of RAM. My monitor is a 30" Cinema Display, bought at the same time (and I intend to keep it). The MP is SLOW, and just putting more memory in isn´t economical; the correct type can still be got at an exorbitant price, but cannot be reused on anything more recent... I do have a SSD as system disk, but that one is indeed eminently reusable... So, need for an update, but the wait for an elusive new MP is too much.
After reading, among other stuff, the Digilloyd and ArsTechnica articles, I ordered the 2.6 GHZ QC i7 Mini, maxed out with 16 GB RAM and a 256 GB SSD (after reading more about the FusionDrive, I think I can do a better job myself of putting the right things on the right disk... ). I´ll need an external cabinet for the less demanding stuff, and a Time Capsule will (hopefully) take care of auto backup; I perform 2nd and 3rd backups manually, to disks kept in a safe or off-site. The Dual-link DVI adapter should work with the Cinema Display. The one thing that worries me just a bit is the absence of a separate GPU, but I never play games....
I anticipate a noticeably faster system, with less heat and noise, and fre floor space under my desk.... Now, let´s see if I really get it....
Gee... Just realised I promised a follow-up after having received, setup, and run the new system. Seems I´ll just make it during the same year....
My impressions so far: decidedly faster than the old setup, MUCH faster download from camera SD cards via the built-in SD slot (had a USB2 reader before), and ample power for LR4 without having to terminate other running software. According to Activity Monitor, 16 GB is quite enough: very seldom less than 3-4 GB free, and no pageouts at all. The lack of a dedicated GPU doesn´t seem to be a problem at all, even with 2560x1600 screen resolution (don´t work with video, and not a gaming person....). And, after several weeks, I still haven´t heard the fan running. The entire setup (Mini, Display and 2 USB2 HD´s) draw just 5 W power when sleeping, 90 W fully running (the old MP station took almost 500 W!). It all rests comfortably on the foot of my CinemaDisplay, dead quiet.
The 256 GB SSD is definitely big enough; the LR database and previews reside there, as well as the entire system and all applications, plus my user Library, caches and all. If I ever need more room there, I could easily get rid of GarageBand, iDVD & c; with their accompanying Application Support files, they are several gigs that i never use. I certainly don´t miss a FusionDrive; I prefer the full control I have now.
Most documents, raw files, and videos are on a USB3 HD (small 2.5", 5400 RPM one) that fills the far more modest speed demands put on it. Also another USB3 HD for auto backups with ChronoSync (as an independent alternative to the TM backup to a TimeCapsule. I also make regular 2nd backups to disks in a safe, plus 3rd backups that are stored offside; I´m a backup paranoiac...).
In short, I got what I wanted, for far less money than a decent MacPro or a MBPR would have cost me.