I've had some issues. Started on 24 just to feel it and worked into vaping all was pretty good. When I got to 2 smokes a day started to get head buzzing feeling at times mostly only middle of day (about 6 weeks in). Quit for a few days and it still happened, quit for 10 days and started to get gut issues like mild cramps in addition. One torch and it was gone so went back to 1-2 a day but dropped to 12 nic, now to 6. Don't get as much effect but seem to be even more sensitive to nic, but 6 is working ok. Going to try no smoke again now that I have some flavors in 6 and one in zero. I've been a little paranoid, all was ok until I quit all the way and I don't want any issues though I didn't/don't seem to have any serious health issues.
So it could have been too much nic was making problems for me, but I needed 24 when I started and it worked fine long as I smoked over 2/day. I did have some headaches and other typical withdraw symptoms as I cut down analogs, which I did over about 2 months and I'm in about the 4th now. I have not had big cravings really, but its not nice when the vaping stops working lol, was happy to get some 6nic and have it work ok. Note I don't chain vape don't have the time to and can't at work, and I only use smaller ego based stuff. That may be why 24 worked for me. I dropped from 24 to 6 in maybe 2-3 weeks with things not working that well, but I stuck with it. It sucked having to smoke so I could vape lol, I was hot. Using some 3 month old ryo tobac, not very tasty either but thats ok.