Started with Blu, and still love their presence and customer service. The flavors have proven very difficult to replicate, but once I felt I got close enough with two individual (and expensive) sets of combined liquids I had to get from 3 different suppliers (LOL) I needed something to start testing them with other than old Blu cartomizers. I still have my batts & pcc's, but I strapped Kangar t4's to the premium 100 batts and i'm in heaven now.
I think for a lot of people the upgrade decision comes when you need to make/try/add different juices or determine a need for greater capacity or vapor production. Because all that aside, Blu nailed it on a lot of levels. If they sold the juice and a tank system, I know a lot of people would run back in a heart beat. I haven't had an analog since Dec 8th, 2013 and I owe that to Blu. They just replicate the experience of reaching for a pack, taking out a ready to go ciggy, and smoking. Furthermore, you're never without when a battery is always charged. This is the longest time in 2 decades i've felt even remotely satisfied with a tobacco alternative and i'm gonna ride my batteries and warranties out, even if they have to serve as backups to something bigger some day.
Right now i'm just struggling with a PCC that holds the t4's out of the box so I can continue that experience. I didn't do this to quit smoking, I did this to quit tobacco, so I very much still enjoy the entire smoking experience otherwise.
Onto the VV question, my background prompts a great understanding of this system. In all honesty, I don't see the need for it when voltage and current have a direct relationship with wattage. I think Variable voltage merely offers you an option on controlling coil burn rate in contrast to say, just swapping to a different coil resistance. Because overall yield at the load (coil) can be altered by changing more than one variable. You can change the presented load, or vary the voltage presented under load. Either will change the final outcome of the equation. If anything I view variable voltage as an opportunity to use whatever coil you might have laying around and get desirable results. that's the final word on that. Hope that helps, first post!