I specc'd UA out of curiousity recently, for raiding, and I have to say... it's only mediocre to me. Like any specc for any class, some players will tell you it's God-mode, others will say it's only for PvP or PvE.
I dropped Ruin and threw in extra points into Affliction. Picked up UA and Malediction, since there's been discussion of how effective 3% more damage would be. I dropped a few things that I do miss, though, in the process. Intensity and Ruin being the most missed in raids... and Soul Siphon from the Affliction tree. Some fights I severly miss the extra bonus to drain life... though many fights it's not even noticed.
The difference between UA and Ruin is based mostly on what the fucking encounter is. On something like Archimonde where you can often be moving, constantly, due to doomfires and air bursts... UA is probably the way to go. You cast it and viola, you have another dot, ticking away. Ruin is nice, but on a fight like that... you can't promise you'll have much of a chance to spam shadow bolts, so it's better to have something like UA to promise that damage consistantly.
However, on tank and spank fights where threat isn't even much of an issue... Ruin does show itself. Lurker, for example, you can pretty much go all out on. I mean the only thing that prevents you from shadowbolting is the brief time you spend in the water during spouts. Otherwise, you can throw your dots up and spam shadowbolts all day while he's up. 6k+ crits add up really quick on a fight like that.
The biggest annoyance with UA is that it's a casted DoT and fairly mana expensive. Corruption is annoying when you have to cast it, haha. UA does it's biggest damage if it's dispelled, as well. Which does not often happen on trash or especially boss fights. So for raiding... I'm debating how worth it, it is. It's not entirely useless, but realistically... it depends on your gear. If you stack strictly plus damage and some hit, then yeah... by all means... stick to as many DoT's as possible. But seriously.. if you go for any amount of crit above 12%... shadowbolts aren't so bad, are they? Especially if you can get in around 20% crit - those 100% damage bonus crits aren't looking so bad, now are they?
I mentioned how on Archimonde another DoT is useful, however... you're still casting it as if it were a shadowbolt, in a sense (not quite as long of a cast time). You still have to be stationary for a short bit in order to place it on the boss. So... it's debatable on how useful it is, even there. It would depend on your luck with Doomfires and such, I'd imagine.
So... I'm pretty torn as to which is better to me. I enjoy Ruin more, but UA isn't treating me too bad. For my current gear, UA is probably more reliable... but once I get more crit - I may go back to Ruin for a bit and see how my damage stands.
I'm not entirely sure on Malediction. I need to go back through some raid stat stuff and see if there's a major difference in shadow damage, etc.
I know there are plenty of other warlock raid speccs and pending where you go or what you're reading, you'll see it say such and such is the best.. etc. I'm not saying UA or Ruin are the only ways to raid, at all. Lol.... just giving my opinion on both since I've raided with either.