Got one myself, can't remember the model. Been thinking of upgrading and buying one of the variable voltage ones.
IMO propylene glycol based liquids are superior to glycerine (VG, as those are marketed), as there is no possibility of a solely propylene glycol/PG-based liquid dehydrating when overheated and forming acrolein, which does seem to happen, as especially when overheated, or heating the last little bit of liquid, at least with the top--wicking kinds I've tried does make the vapor caustic and choking, feels exactly the same, if to a lesser degree, than getting an airway full of acrolein vapor. It isn't the nicotine certainly, as this caustic change occurs in all glycerine based liquids I've tried, weather they contain nicotine or synthetic cannabinoids.
Of interest, at least my local head shop has been getting inventive, one of them is now packaging the synthetic cannabinoid STS-135 in a vaporizer liquid. A good choice too IMO, of one to use for that, given its high potency. A few tokes of that, as an ostensibly 1mg/1ml blueberry flavoured liquid is enough, and even after a fill has been used, enough clings to the wicks to make it last quite a bit longer.