Unless you're going after systems with > 4 core, MacPro is practically a horrible deal.
A quad MP costs $2500, even with a $2000 refurbished deal, you get a system contains an old Xeon, a mere Radeon 5770/5870, USB 2.0, no Thunderbolt, not even SATA III. Means you can't even get a full transfer speed with full SSD. It is hardly capable and a bad investment for 2013.
Maxxed out 2012 iMac will always be a better deal. Cost roughly the same and it comes with the monitor, cheaper AppleCare plan, practically better CPU/GPU, also it has USB 3.0 and Thunderbolt for much faster interface.
Hey I love MacPro for being a real desktop. But Apple certainly want it dead, collecting dust in the corner of the Apple Store.
I have 6 cores on this Mac Pro... And for 95% of the time the system is waiting for me. On those rare occasions I actually make my system work hard the "old" Xeons probably waste, oh, say 30 seconds to maybe a minute at most. I've got 16GB of RAM - which I can and will eventually upgrade - though maybe not up to the 32GB stated max. Often the stated max is Apple's "we won't support more, but - go ahead - it works."
I can drive up to 3 professional monitors on this Mac Pro out of the box. I won't need them, but I can add another video card to drive more monitors.
I already have several terabytes of internal HDDs for data storage, and have room for more as I need them. I haven't yet played with an SSD since the price per GB is still dropping, but I'll only need one of them. It's the massive amount of internal storage I need. I don't really see a big advantage to SSD. My system stays on for days, weeks at a time so there is no boot time. I generally keep most of my applications open all the time too, so there is no lag time there. The time it takes to load a dozen photos into Lightroom is about 2 or 3 sips of coffee. I can live with that.
I don't need USB3 since I'm already invested in FW800 peripherals. At the moment I don't actually have anything that uses USB3. But that is just a cheap card that needs inserting when that changes.
For Photoshop work the basic GPU is already overkill. I'd rather use the money saved on camera gear.
I use both ethernet ports on the Mac Pro. I don't bother using WiFi on this system since I use ethernet to connect to the router - partly distance, and partly because sometimes I like to zing a file to or from another computer in the house. We have Apple routers which are gigabit speed, so WiFi is snail slow comparatively.
I use the 2nd ethernet port to connect to either a) my printer - because the ethernet cable can be much much much longer than a USB cable, and I have big printer that doesn't fit into office, or b) the computer that I tether my camera to when I'm shooting. (I shoot into this 2nd computer because it powers the camera via FW, and it can store way more than a CF memory card.) After the session I hook the two up via ethernet and move a GB or more of photo files to my Mac Pro.... and that transfer is fast. That time savings is more than I would see with a "newer" CPU.
I believe that Thunderbolt is a technology that I won't ever be able to use with this system. Too bad, 'cause I think it will have a lot of potential. But it's not like there is a lot of compelling reasons to get it yet. The technology has not yet caught up to the potential. Maybe when this Mac Pro retires?
So - on a speadsheet listing features it may appear that the Mac Pro is old and tired, and being out run by an iMac... but for those of us who need a solid workhorse the Mac Pro is still a seriously good investment. This is a professional machine that is designed to work and work. And when it doesn't work - to be fixed and then start working again.