Cards on table: I voted "terrible". I would like to elaborate, however.
The current change obscures rather than enhances abilities that can be used. Because the cooldown glare thing is so bright, it draws your eyes to exactly the abilities that you can't use at the time. This is made even worse by the fact that it shows this eye-drawing animation for global cooldowns in addition to "real" cooldowns. It's basically a minor case of information overload. The overarching principle should be: Show me what I can use, not what I can't. The current implementation fails this test.
The goal of this UI change is to enhance contrast between usable and on cooldown abilities. I get that. But the solution is to make usable abilities brighter or unusable ones darker...basically the opposite of what was done.
In an attempt to be more forward-thinking, if you want to improve the action bar UI, the next thing you should consider should be calling attention to reactionary or otherwise special use abilities when they become available. For instance, if I can only press a button when a mob is stunned or dotted, that button should flash at me when that's happening. That said, that's a different problem and somewhat off topic.
The previous action bar UI wasn't perfect, but the current iteration is worse. I humbly request that it be reverted and action taken in another direction.