Personally, I experience dry mouth and a film of PG liquid develops on my gums after vaping all day. I'm prone to migraines, so the dry membranes in my nasal cavities scare me, since that area is important to the sinuses and many of my sinuses are sinus related. However, I don't think the dry nasal cavities have ever actually developed into the dreaded headache.
After a while I learned to keep myself well hydrated, like the others in the thread have said. So I carry around a water bottle with me everywhere I go. I have cut down on drinking soda, since I'm rarely thirsty when the opportunity arises. This leads me to believe that vaping is forcing more healthy lifestyle choices on me than just cutting out combustion cigarettes. I've never drank as much water as I do now, and I actually feel a lot better as a direct result of that.
The film that develops on my teeth and gums, however, bothers me because I believe it will have some detrimental effect on dental health. I'm waiting for more studies on vaping to determine the non-lung-cancer related effects it has, like does it eliminate the risk of gingivitis caused by smoking analogs but increase chances for cavities and dry mouth related problems?