If I want I can run it as fast as 2600 rpm and get temperatures as low as 45 celsius in the game. The aluminium back dissipates heat very well, and the fan, is more than enough. The cooling is far from being terrible, it works very well. I do not know the frame rate, but never, never lagged or made me feel the machine is having a hard time running the game. The game was smooth and never lagged, it worked wonderful from the beginning to the end. The computer noise level at minimum, barley hear the fan. Cpu temperatures.around 65 gnu around 70. I played Akram city on native resolution, everything on high. My config is like this: iMac 2013, 27'' i7 3.5ghz 780m and sad, 8gb ram. The thermals on the new imacs are terrible as well, so a loaded cpu and gpu will be sitting at base clocks under heavy gaming I am guessing, rarely getting to their full potential.

I'd say it's good/ok for current games, but without the ability to update, that 1440 panel is going to need a lot more muscle than the 780M which is equivalent to the 660/660ti on the desktop side which is already inadequate for high detail gaming at 1440. It doesn't take much to do straight 2-D CAD but once you start getting into high detailed rendering then those things slow to a crawl. There's a good reason why Autodesk products haven't appeared on Macs in almost a decade. A very expensive shot for the hardware included. In additional to a priority being placed on aesthetics over function, you really aren't able to service it yourself nor are you easily able to upgrade parts, so it's kind of a 1 shot deal.

We have a few with the 3770's and 680M gpu's and as soon as any load is put to them, the cooling system is immediately overloaded.

As soon as a 3d program is loaded up, the computer just about melts down. I've had several iMacs forced into my architecture office by controlling partners, I handle IT as a side-role in the firm, and they are fine/great for people who don't need an additional screen(a matching screen from Apple will set you back a pretty penny), and aren't doing much beyond graphic design or light drafting.

Imac 27 late 2013 780m