This is just a few bugs I've experienced or seen reported by multiple sources. Feel free to add your own (confirmed bugs, not gripes):

Vertical tiling is gone, it will only tile horizontally
Using 'scubby sliders' when recording actions inserts a separate action for each increment (sometimes hundreds)
Large brushes (hundreds of pixels) are disproportionately slow
Plugin search has changed, so plugins with many folders can make booting very slow
16bit editing sometimes looks worse than 8bit (this really isn't a bug since its out of Adobe's hands, the files are fine but video displays vary in how well they handle it)
Document windows sometimes get stuck up under the menu so you can't move or close them (usually after minimizing PS and then bringing it back up)

There have been many reports of CTRL key problems, but this isn't a bug, it's from using a pirated version (so don't report it here or we'll know about you :) )

1. I ran into the problem of the window betting stuck under the menu. Minimizing didn't work for me. But what did work was to tile the window.

2. Now, most people would not call this a bug. But if you think about it, having more than 25% of your viewing area disappear for no good reason would be considered a bug if it happened out of the blue. What I'm talking about is the Shadow/Highlight adjustment menu. This could easily be made much smaller by reducing the throw distance of the sliders to the same standard as the older sliders. And the layout could also be organized in a more compact way. IMO, there is no excuse for wasting screen space the way this menu does.

3. Technically speaking, the control key issue is not necessarily related to pirated software. There are some people who pay their money and resent activation. So they try to get around it. And, of course, I'm sure a lot of this is also pirating.