I've tried tobacco absolute and and was not all that impressed. It comes as a thick dark treacle like substance that has to be warmed gently to becoming fluid enough to work with. It is "EXTREMELY" strong and has to be diluted to the nth degree, and requires a good deal of steeping to settle down and even then it will not be what you're expecting. Its adds an green slightly cloudy hue to the eliquid. It did provide a good throat hit and did impart a sort of hard to place tobacco hint that is missing from normal tobacco flavoured e-liquid. But the decision not to bother with it, based on what I say below, was no real loss.
There is a fly in the ointment with tobacco absolute. It is not designed to be ingested and it is a known chemical irritant. I mixed my first batch slightly too strong and made my lungs burn like I'd knocked up a batch of lime mortar. I got it from Perfumers Apprentice so its from a reputable source and I thought I'd mixed it pretty weak having added two drops in 20 ml pg and then added 2 drops of that to 10 ml, maybe there was a concentration at the top of the bottle or some residue floating on the top, who knows, but I was mighty relieved when the sensation improved although it took a couple of days for normal vaping to resume. It may not have the same toxicity as smoking however toxicity is not the only consideration when inhaling things. Asbestos is not particularly toxic to eat but its a bugger in the lungs.
I worked in court dealing with industrial accidents and diseases and frequently had cases involving lung diseases using a burden of proof of "the balance of probabilities", i.e 50%. This allowed medical expert witnesses to provide their evidence based upon the best of their knowledge rather than absolute proof and many were suggesting that persistent lung irritation even by non toxic substances could be a source of potential problems. These arguments often arose when the substance in question had no proven chemical or particulate interactions. Given that you're likely to be puffing away on this stuff day in day out adding a chemical irritant is not such a good idea in my opinion. I have no direct evidence other than my personal experience and the fact that tobacco absolute is a known irritant and continuous exposure to lung irritants isn't a risk free enterprise.
Of course the other downside to the use of tobacco absolute is that if its use becomes widespread in the vaping community it is likely to provide ammunition for the regulators as it is not approved for ingestion, as most other ingredients are, and does contain some less than appealing substances. Its a vast improvement on tobacco smoke, and lacks many of the hideous toxic chemicals added by scumbag tobacco companies and the process of combustion. However it is a massively concentrated distillate of tobacco producing an essential oil designed primarily for use as a perfume ingredient. If it transformed the vaping experience I'd be more inclined to take the risk as I'm by no means a risk averse mung bean eater, but it doesn't in my opinion, and I would love a vape that hit like a cuban cigar. So for me I'll stick with my half arsed ersatz tobacco e-liquid and accept the compromise. I'm not attempting to scare people off tobacco absolute, mixed in the correct quantities most vapers don't report problems, but just because you mix it weak enough not to notice doesn't mean its not having an effect. I cannot quantify the risk, and life is full of risk, just be aware that we're in uncharted territory here and tobacco absolute is not a food flavouring like other e-liquid ingredients.