I purchased the Cig2O from the local shop, and to honest, I have been very pleased with the results. After reading through and studying the information here, I believe they have upgraded their carts. I am using the 18mg Tobaccco carts. Experimenting with an empty one, the cap pops out easily, and should be good for refilling. The batteries are a little different, as best I can tell. Vapor4Life carts do NOT work well with Cig2O batteries. The vapor and flavor was very inconsistent. After discussing the issues with V4L, they said that their carts are NOT 100% compatible. (I was told they WERE 100% compatible when I talked to them prior to buying). Also, the V4L carts taste very sweet, and resemble burnt caramel. I didn't like them at all.
I will say that the recharge case from V4L works great. I keep 2 carts and a spare battery in it, keeps it charged and ready to go. I was able to swap batteries in and out about 4 times before the case battery needed recharging. It wasn't the 8 times they advertise, but was still well worth it to me.
Right now, I'm looking for the factor Cig2O juice so I can refill. If anyone knows a good place to get this, I'd love to know.
Happy vaping!