Still a poor choice for photographers.

From a reading of the specs of the latest iMacs, the reasons to upgrade are:

• You do a lot of moving of large video files. The new Thunderbolt connector is 10x faster than USB but peripherals using it are rare and only just coming to market.
• You need three displays. Existing iMacs can support two (iMac + 1 external). The new ones can support three (iMac + 2 external) using Thunderbolt. Once again, the only displays currently using Thunderbolt are the overpriced and glossy-only ones from Apple which simply cannot be properly calibrated for serious photography use. Once it becomes available, a good Dell matte display will be half the price of the add-on Apple one, the latter too garish/bright/contrasty, just like the display in every iMac since they went all glossy four years ago.

The modest CPU and GPU speed increases are not a compelling reason to upgrade.

Further, AAPL still has issues with graphics cards overheating (which killed both our white non-glossy iMacs and made me build the Hackintosh – these were the last iMacs with a screen that could almost be properly profiled for photography use). Still? Well, yes. Why do you think the iFixit tear down shows that the graphics board in the latest iMacs is removable, rather than integrated on the motherboard? Because they expect to replace many, testament to the poor cooling of the part in the tight confines of the box. Form over substance design continues at Apple. Plus, as you need to remove the motherboard to access the removable GPU, you need to be very skilled or very lucky. And then where do you get the replacement? It simply does not solve.

Click the picture for the iFixit teardown of the latest iMac.

If you need a good photography machine and must have Thunderbolt, the best bet is to wait for the Mac Mini to add that connector and hook it up to a couple of proper displays from Dell. Or for higher speed, build a Hackintosh.

Save your money unless the above are compelling reasons for you.

The single best thing you can do to make your iMac significantly faster is to add a Solid State Drive for the OS and applications. It can sit externally – internal installation is sheer hell – and you tell System Preferences->Startup Disc to make the SSD the one to start from. Install OS and copy over apps and you are set. You continue to keep data on your existing internal HDD which is big and cheap. The SSD is small and costly but it dramatically increases start-up speed and application loading. I added an Intel SSD (only 128gB) to the Hackintosh and the difference is night and day. I use maybe 50% of it – OS + apps only. Far more real world performance increase than newer CPUs or GPUs. It cost me $225, and prices continue to fall. Once you have used an SSD there’s no going back. Also, an SSD has no moving parts – always a good thing.