I use the Thunderbolt port on my iMac. Best thing ever for external storage.
Me too. I always preferred it and use it mainly for backup drives, OS installers, boot drive for a second OS installation... And also sometimes to connect a MacBook Pro or Air for migration.
It's just much more reliable and always fast. With Thunderbolt 2 and an external PCIe SDD you could even get near the speed of the much overpriced internal SSDs. USB 3.0 can't even get the full speed of a standard SATA-III SSD.
And especially the 5K Skylake Late 2015 iMacs still have strange unfixed USB 3.0 issues. I also often heard about USB 3.0 problems on other Macs too since El Capitan.
I use those ports only for my two Logitech USB receivers that came with the solar keyboard and a very old mouse, also for my iPhones to backup/sync and for my printer. None of them need USB 3.0 and work without any problem.
But USB 3.0 is just horrible on that iMac. There are many problems like slowing down to USB 2.0 speed or random disconnections.
It's packaged at the moment because I am moving so I could not test 10.12 yet on that iMac but they did not manage to fix those issues until 10.11.6 beta 2.
There are some nice monitors from Dell and LG that connect via Thunderbolt and even at least one of them uses Thunderbolt 2.
But if I remember correctly none of them is 5K and the screen size would be 29- and 34-inch or even curved. All of them just does not match in design, size and resolution.
A 27-inch 5K from Dell would waste both Thuderbolt 2.0 ports with a Displayport 1.2 connection what is also no good solution.
Using a second 5K iMac to match the design completely does only work if you run it with it's own OS installation because there is no possibility to connect the two displays.
Really sad...
I remember when the 2013 Mac Pro was released, Apple already began selling a 34-inch LG Thunderbolt monitor in their own online store. At least in Germany. Maybe they even had them in their physical stores as well back then but I don't know.
That was the first sign when I thought there will never be a new Apple display again. I think they only stopped selling it because of the 5K iMac. It had been there for quite a while and some other authorised resellers that only sold almost the same stuff as the Apple store also sold that monitor.