Shadowstep > Ambush = overpowered. I've one-shotted clothies a couple of times doing this.
I leveled combat, but I used daggers because they suited my play style better. I played a thief/ninja in FFXI for 5 years (where "stealth" actually cost reagents), so i am daggers for life. But that's just my play style.
At 60 I decided to try a respec to Sub to have a little fun with Shadowstep for a couple of levels. Well, I respecced and I can tell you that I will never go back. I went Hemo-Shadowstep. I still use daggers, and I know the "cookie cutter mass majority" says that's a no-no, but it works for me better than swords did (yes, I did try them for a while). I'm one of those ambush openers that are so rare these days, but my ambush crits are insane as is. Add a shadowstep to that ambush and I make clothies cry.
Now, hemo doesn't do as much base damage with my daggers as it would if I were using a sword, but one thing about hemo's debuff is that all 10 rarely get used up before the next hemo is applied. In PvE, I've found daggers with hemo to be godly, but once again, it suits a play style that I got used to for 5 years. Faster daggers, however, let less hemo's go to waste. It's fun for me, still contributes to my groups, and I still continue to top the damage meters every time. Doesn't work for everyone though.
Anyway, back to PvP...
My favorite part about Shadowstep is fighting those pesky mages. I'll stealth in, CS, throw a hemo, beat on them til it's time to KS, beat on them some more, until they wake up. At this point, assuming they were stocked up on stamina, they are running low on health (non-stamina stackers would be dead by now), so they do one of 2 things: Frost Nova or Blink. Blink is great because they think they are getting away, this is where I Shadowstep > backstab which results in their death. Frost Nova is great, because if CoS isn't up, you can still shadowstep. It's funny because you take the frost trap with you, but if they have stopped running to cast then you appear right behind them ready for a backstab.
Locks are a similar situation except that they usually throw a how of terror instead. The great thing about fear is that it removes you from combat, so when fear wears off you pop a CoS and re-stealth. Shadowstep behind them and if their health is low then ambush, if they still have quite a bit of health then commence stun-locking.
That's just a little taste, but honestly, I think ShS is a great build for PvP. I dominate now much more than I ever did combat (especially combat swords).