I just received my BSB and vaping at 3.7. This thing blows my eGo away...and I love that thing! I cannot wait for my 6v setup to charge! So far this BSB gets a 10/10 from me. 

I was previously a 6v only user, but I honestly would not advise 6v on the SB. It leaves a burnt taste to the juice, but a monster throat hit. If you are looking for better throat hit grab up a double barrel tip.
Glad to see you like the SB though, I love mine and could not imagine life without it now.
I am really looking forward to getting a dbsb top. I am planning on a dbsb with cartomizers for when im on the go, should be fricken awesome!
Have you tried using 6v with your 510 cartomizers? It is said the resistance is higher than regular 510 atties. Maybe that will cut down on the burnt taste.
I am getting a couple of 3v batts just to check it out. I'll be buying non-rechargeables from wally world in case I don't dig 6v. Small investment.