I love Deception/Infiltration, and the rework to make the spec viable made me very happy. The downside is that a Deception Assassin is very squishy, making them a "glass cannon" build. Yes, they have decent defensive CD's that can help in the start of a fight, but in a prolonged engagement they wilt very quickly.
As mentioned in another thread, I mostly enjoy the "Bruiser" style of gameplay, and the other day I got back on my Assassin and decided to go back spec Darkness. It was just how I remembered it...great. =)
Darkness will not pump out much burst and is not really good at taking out healers by themselves, but they do provide a great amount of team support in mass battles as well as making for arguably the best solo node defenders. And its been fun to be a beast again who can widdle an enemy down faster than they can widdle me down.
The method of spec'ing Darkness and wearing DPS gear is still viable, and is what I'm doing (using a Shield Generator instead of a Focus though). And it allows for some decent constant damage (not much burst though) while also providing a good amount of defense through Armor and Shielding. For reference, an Operative and myself were able to defend the mid node in Alderaan from about 5-6 enemies for a very significant amount of time due to using LoS and the high number of AoE attacks the Darkness Assassin has.
So if you've got an Assassin you want to take for a spin in PvP, but don't want to get blown up, try Darkness. Its nice!