I recently received the following:
27‑inch iMac
i9 3.6GHz
8GB RAM (I've upgraded it to 40gb)
Radeon Pro Vega 48
512GB SSD
Magic Trackpad 2, Magic Keyboard 2 and I'm using a Logitech MX Master 2 mouse in conjunction with the trackpad.
I'm blown away by this machine. I was using a late 2015 i7 4ghz and m390 iMac prior to this one and the difference in performance is huge. I've also paired it up with the LG 5k Ultrafine monitor and the two work perfectly together and since the Ultrafine has three additional thunderbolt ports it somewhat makes up for only having two thunderbolt ports on this iMac, which is one of the drawbacks this has as compared to the iMac Pro.
The Vega 48 is also more powerful than I was led to believe. After a gaming session I did a Geekbench test and got an OpenCL score of 150996 which is a bit higher than the scores of around 142000 which are on the Geekbench list. I think these people must not be allowing the GPU to warm up when they're running the benchmark because after it gets warmed up I'm consistently hitting 148000 and above, which is great. It performs great in games as well. I've been running Mad Max, Middle Earth: Shadow of Mordor, Alien: Isolation and Borderlands 2 at 4k resolution, maximum settings and they all run well. I've also been playing Subnautica, Everspace and Rise of the Tomb Raider at maximum settings and at 3200x1800 resolution and they all run smoothly above 30fps; likewise the recently released (for MacOS) Black Ops 3 runs smoothly at max settings at just a bit under 4k. Deus Ex: Mankind Divided was playable at max settings and 2560x1440 but I don't think this game is well optimised for the Mac because it doesn't look that great but seems to be very taxing on the system. It would probably be better in Windows. In fact all these games would perform better in Windows, but at the moment I'm just playing them on MacOS. It's also good fun going back and playing older games in 5k like Batman Arkham Asylum. The ultra high resolution breathes new life into these older games, though there is screen tearing, so it's probably still better to play at 4k. I will say however that modern games do cause the fans to blow pretty hard, but if you play with headphones the noise isn't a problem. Also, 32gb or more is a must for some of the more graphically intensive games like Rise of the Tomb Raider at max settings. While playing that my ram usage was around 23gb.
For the i9 processor I've hit 6191 on single core and 34187 on multicore on Geekbench which is only a little behind the multicore score of the 10 core iMac Pro and better than the 8 core iMac Pro. That's incredible for the price! And during everyday usage the fan noise is basically silent, which was often not the case with my previous iMac. In my country (Australia) I've save about $1500 by buying this instead of a base iMac Pro. With that money I've been able to add on additions such as the Logitech Brio 4k webcam which is a much better webcam than the iMac Pro's, more Ram than a base iMac Pro, an external SSD and still have a $1000 left over. The Vega 48 is only a little worse than the Vega 56 (probably 5fps or so in most games or you can probably run games in a little higher resolution); the difference in price is not worth it for the Vega 56. Apple have done very well with this product and I think it's the best value product they're currently selling.
