[nickyp]

Basically: people who need to fill the slots to connect hardware that's as expensive as their computing platform and/or are running a software stack that can also cost as much as an iMac. In generally these people fit the 'Pro' suffix ;-)

High-end multi-channel audio interfaces and/or audio processing cards that accelerate audio plug-ins. Even Firewire or USB equipment works best if each device is using dedicated controller cards. (every Mac has only 1 USB/Firewire controller)

If you need to connect multiple 30inch Cinema Displays and still have proper performance (e.g. 3D) you need multiple GPU's. These cards often get replaced after a couple of years to boost performance.

And most often these kind of applications demand a lot of (very performant) storage so RAID controllers and lots and lots of hard-drives come into play.

If you're not buying a Mac Pro for these kind of workflows, you're just shopping for bragging rights I guess ;-)

And trust me: if you're using a Mac Pro in this manner you're not jealous about that very speedy iMac with that really nice display. It might me speedier, but it just can't do what your workstation was bought for.

And hey, maybe you'll buy one for the 'light web browsing' in your den ;-)

[bhousel]

One other difference: the Mac Pros use ECC memory, the iMacs do not. This makes sense, given the users that each product line targets.

[Tamerlin]

Good point.

That probably adds quite a bit to the cost of the machine.

I realized after the fact that I implied that the creative industry was the ONLY other one that would be interested in a MacPro rather than in an iMac, rather than just an example. Oops.