Guess I'll chime in. I am one of those that purchased the
quad core i7 Mini Server and a Thunderbolt display, and
can say that I am quite pleased. The prime use is as
an engineering workstation (hardware/software/firmware)
and as such, it performs quite well. I can have a Win7
virtual machine running with development tools and or
diagnostic hardware and OSX tools at the same time and
have not had any issues.
When not used for work, do some personal photo work
with Photoshop and some simple video work and works
good enough for me. I can see where the graphics card
would be an issue if someone did some really heavy
duty stuff in Photoshop. But, that would be someone
doing pro work which shouldn't be messing with a mini
anyway.
I decided on this approach because if I retire the Mini as
a work machine, I can easily and conveniently stuff it on
a shelf somewhere and use it as a server. The early 2009
iMac it replaced is not that useful and sits as a backup
should something fail or maybe find a buyer for it.
Ps. The Thunderbolt display decision was also based
on the fact that I could use it as a dock for my MBP
if I desire.