I work as an EMT, and have been very cautious about my health, its been about a month off now.
Negative affects: vaping has the potential to dry out your throat and making it very sore however I got a upper GI series xray that shows there are no perminent damage, its just really sore from drying, Another danger is pleural effusion, over moistened spot in the lung, or pleurisy (dry spot on the lung) this is caused not only by the moisture form vapor, but from the chemicals left from tobacco clearing out of your lungs. I dont think it is very common however, and again leaves no perminent damage, it pressents as chest pain, Negative pressure can relieve the pain (exhale hard without exhaling, kinda like when you plug your nose and blow to equalize pressure in your ears, only for your lungs)
Nicotine, can cause some known heart problems, but the general consensis is you get less from vaping then from smoking. However there does seem to be more of a suppression of appitite from vaping (i dont know why just my experience)
Positives: within the first week you will start to have more energy, and generally feel better, soon after your lungs will start to clear out, and you may feel sick and have difficulty breathing, exercise, lots of fluids, and good diet are very important through the "cleansing" stage. it can take as long as 2 months to fully clear out your system (depending on how much you smoke) but after you are totally clear of tobacco and adjusted to vaping, you should feel great! like a non-smoker, save the nicotine.
These are just my opinions and observations of mine and others experiences