I think and as many thief players think, Anet took many good aspects of the class away, and as a result they left us with very little option to choose.
There are not much variety among the builds imho. And mostly you are limited with your own play style/skill level.
In terms of traits, almost in each Thief trait line there is only one ideal combination (maybe except Deadly Arts) and rest of the combinations are simply meaningless.
But in general, Thief traits seem to me quite weak, ineffective.
Just some minority of them are better than the pointless majority.
Same applies to some Thief utility/elite skills too (and also some weapon skills).