I never talked about this before because I didn't want to offend anyone...but...
Before I found V4L I had really built up quite a stock of 510 batts. So when I changed over to V4L, I felt like those 510 batts were a waste of money. Just like so many others, I tried using adapters, but the hit was way too airy, and I just couldn't get the flavor & TH that a VK gave me. So I just let the 510 batts sit.
Well now that the 510 cartomizers have been released, I am definitely glad that I never sold my 510 collection. These 510 cartos are great as far as I'm concerned. They really do seem to last forever. I consider myself a pretty heave vaper, and I can get one of these 510 cartos to last me all almost all day. And the flavor & vapor is really good too.
VK cartos & batts will always be my favorite. But these 510 cartos give me a chance to give my VK batts a rest. Also, it gives me a chance to use some of my liquids I had bought from other vendors before I started buying V4L juices.
Overall, I'd say that if you have a 510 collection, the 510 cartos a a great
buy. But I wouldn't ever consider changing over from the VK to 510.