Video game audio. He does all of our audio work. Sound effects, voice over, music composition, etc. I asked him what audio he used and his answer was Pro Tools, Digital Performer, and Peak. He's got a super top of the line Mac Pro that's only 2 years old and he's been salivating at the prospect of an upgrade for a long time.

He was extra pissed that the new machines don't even have Thunderbolt. He has many hundreds of gigabytes of audio libraries on a variety of external storage devices and just having Thunderbolt would be a pretty decent productivity improvement.

You can never have enough processing power when you're editing and re-rendering videos.

Hell, I find lightroom able to use all the CPU I can throw at it when I muck around with ~400 photos that I shoot in a day.

I have no doubt that video work can easily use all the CPU/memory you throw at it: imagine rendering a finished video in five different formats and resolutions in the background, while you're editing/tweaking your next project in the background.

Remember these are professionals.

Probably the ones who have 32gb of memory for their photoshop scratch buffer. There's still quite a few of these types of professionals. You just can't put that much memory in the Macbook Pro. Processor speed is probably less of an issue compared with memory capacity.

All of the above. Audio, video, 3D. Any pro level design. Even print design.

Having a Mac Pro with lots of storage and big monitors when you're working on a 300 page book with 300GB of photos is much less annoying than poking along with a laptop.

It's not just the speed, it's also the usability. Eg, a comfortable trackball and a nicer keyboard. Sure, you can add those to a laptop, but then you have a kludge.

Audio professionals editing large surround sessions with lots of plugins and lots of tracks for one (plus you need 3-4 or more PCIe slots to stick Pro Tools or similar DSP cards in). These need as much horsepower as you can throw at them.

Video professionals doing rendering or compositing, ditto.

Not to mention the video cards available, plus being able to throw four full size drives directly on the SATA bus.

What everyone else said, plus the fans. Man, there are times I actually think about a Mac Pro as a humble Rails developer. If I fully parellelized my test suites it might even be worth the money.

People in the business of video editing are one example. They need/use more RAM and processing power than you can get on any new model of Macbook Pro.

I imagine he is talking about sound engineers. Also, he is talking about the Mac Pro (the desktop) not the Macbook Pro, the laptop.

FX artists for digital cinema. 4K takes nearly half a gig a second uncompressed.