I have some free time (queued up on Illidan) so I thought I'd make some suggestions from my experience so far, some of these are purely aesthetic.
- Soul Fire: It would be nice if Soul Fire would cast through my stance dance like Harvest Life channel does. During <20% nuking it can be hard to guage how long the boss has left, how much Fury you have/will have and will burn through and when to start spamming Soul Fire in Meta, and that's when this can become an issue
- Burning Rush: I like the idea of the ability but the effect doesn't look burning at all, just some white air tails indicating speed. Our Glyph of Nightmares gives our Dreadsteed a trail of fire behind it, I don't see why Burning Rush couldn't have a similar graphic considering the name and effect of the ability.
- Glyph of Shadowbolt: I've said it again and again, but one more time; the graphic is too small! Sure it used to be too big, but now it's too small! I want to SEE the Shadowbolts, increase the size ever so slightly and I will be happy.
- Void Ray: I don't know where to begin, I don't like the way it looks, I don't like the way it works. I often have the time to throw Corruption on multiple targets but they're rarely stacked on each other leaving my only real option for AoE filler as Harvest Life. Personally I think the ability should be completely reworked.
- Demonic Leap: It's buggy. Sometimes I jump backwards for no reason whatsoever; i.e. I'm on a flat surface running forwards and... I jump backwards?
I'd also like to say that I'm really enjoying myself playing Demonology right now in 5 mans, I think Blizzard did a great job on this spec (and others) and most of these issues are pretty minor considering the entire spec as a whole.