Radeon R9 260 

I wish I could offer more input, but I just found out about it and it seems pretty cut-and-dry: if you had problems, they should be fixed.

We expect to see official details of the R9 300-series of products of which there have been many leaks as well as the final details of the AMD Fury and Fury X products based on the new Fiji GPU.

The experience was smooth though of course there were no indications of frame rate, etc. while it was going on.

The current rumors claim that Fiji XT will have 4096 graphics cores that are fed by a high-bandwidth, stacked memory architecture, which is supposedly rated at 640 GB/s (versus 224 GB/s of the GeForce GTX 980).

That said, they also have cache and other methods to reduce this dependency, but let's just say that, if you offer a graphics vendor a free, order-of-magnitude speed-up in memory bandwidth - you will have friend, and possibly one for life.