I have had my Xhaler for a little over a week now. In the past i have tried the 901, 510, and the kr808(v4l) Its pretty safe to say that these are now sitting in a drawer. The Xhaler is simply AWESOME. Tons and tons of vapor, Major throat hit, excellent flavor! I tried both the 510 adapter and the kr808 adapter. I find the 808 cartomizers to be by far the way to go. I can take long hits and get loads of nice warm vapor. I have refilled the same cartomizer 10 times and it is still going strong. The 510 adapter seems to have a lot less flavor and throat hit. So if you are considering buying an Xhaler, my advice would be to go for it. My one recommendation would be to get a couple of spare batteries because they take a while to charge