its also not true that it hasn't been studied.

I didn't say it hasn't been studied. I said "Right now we do not know the long term effects of e-smoke." It's true. We don't know. We don't have hundreds (or even tens) of thousands of patients that have been using e-cigs for 20, 30, ... 50 years like we do with other drug intake methods.

Rather than explain it fully myself, I can cite the well-written conclusion from Priscilla Callahan-Lyon of the FDA (Tob Control. 2014 May;23 Suppl 2:ii36-40.; I emphasized the many statements of uncertainty to make the point)

Although e-cigarettes have potential advantages over traditional cigarettes, there are many deficiencies in the available data. ... E-cigarettes may be useful in facilitating smoking cessation, but definitive data is lacking. E-cigarettes may provide a less harmful source of nicotine than traditional cigarettes, but evidence of decreased harm with long-term use is not available. It is encouraging that few serious adverse events have been reported related to e-cigarette use during the years the products have been available, but without a specific reporting mechanism, adverse event data may not be comprehensive. ... Significant gaps exist in the health-effects data for e-cigarettes. Product standards including criteria for ingredients, quality and manufacturing have not been developed. There are limited data on the effects of recurrent long-term exposures to aerosolised nicotine, flavourings and PG. The effects of an aerosol delivery system on the quantity of nicotine consumed by users are unknown.

The paper is actually a great review and it's freely available from PubMed Central. Here's a link.. If I had to place money on it, I'd definitely say e-cigs are safer than conventional cigarettes. But I stand by my initial statement: we do not know what the long term health effects are.