Here’s the skinny – Aperture 3 ran fine on every machine in the store, ranging from the lowly Macbooks to the beastly Mac Pros with the beastly 30-inch monitors. I played around with a lot of things, stuff like switching views, playing with adjustment brushes, making level and curve adjustments – all the regular stuff people do with Aperture.
However, on the lower-end machines, Aperture was a bit slower when it came to handling the huge RAW files that originated from medium-format backs. Smaller RAW files from Canon and Nikon cameras were fine, but the 60-megabyte+ portrait files from the Leaf Aptus were a big drag on performance. For example, when using the skin smoothing brush, it would take a few seconds for the effect to register on the screen. This isn’t a real problem because anyone with a digital medium-format back is almost certainly using a very powerful Mac and isn’t even using Aperture – they’re probably going with Capture One.
The bottom line – most Macs will run Aperture 3 just fine, even a little better than Aperture 2, which works great on my early-2008 Macbook.