I use a modified SM/Ruin build, and it serves me great!!!!
I respeced to Felguard, then decided to logout and play my hunter for a while(this is a joke to all the Felguard lovers). Actualy I am in love with a lot of the demo tallents, and am so sad to not have them, yet I got over it....... I knew that if I was not happy with demo, Distructo would be worse, so i tryed it (I had one respec from 1-60, so they were cheap)Turns out I liked the distructo build, haveing drooled at conflag for so long, it was nice to use it. 3 AV's later and I realised I did better as SM/Ruin.
I was not quite done yet though, I had to try out UA. Watching folks die as a result of pressing Clese was funny, yet 3 weeks in to the new tallents most folks learned how to just heal the dammage rather than clean the debuff, and honestly if they do not dispell UA,it is not that great of a spell. Sure it is nice in a raid envinroment to have a extra DoT, but neeeded? not as much for me.
I have yet to see a lock build that I find as amusing as SM/Ruin builds, For me it the synergy of SM,Nightfall, IMP SB and Ruin that realy dose it for me. The build is strong with Cirt and with spell dammage gear or just about any mix of the two, the build holds some thret reduciton on the affliction part of your dammage(proactively cutting aggro is good), as well as leaving you a real heavy hitter. Personaly none of the 41 point tallents shined very bright once the newness faded. some folks love em, but I like the way I am. Overall, I have to admit though, I do not perform as well as i once did. SM/Ruin was awesome, I could hang with either the PvP'ers or the raiders, my build gave me strenght in both areanes. Now a days locks with a 41 point tallent Tend to outperform me. I just didnt find the playstyle of the new tallents up my ally.