Well, weīve found students taking to it like ducks to water, as have other FTOs.
You donīt have to do differences training to fly it - any more than you have to do differences training to fly any other aeroplane in the "class". Most people only train on 1 multi-engined piston aeroplane and then move up to the next stage.
However, you do need to do a short stint of training (couple of hours maybe) to allow you to fly archaic, multi lever aeroplanes, but whatīs new there? Do you think that if you train on a Seneca you can REALLY fly a Duchess or a Cessna twin without a couple of hours familiarisation? Would an organisation that operates senecas let a Duchess trained pilot loose in their aeroplane without training and a check ride? Of course not, and the same applies for going from DA42 to avgas power and back again.
Of course, you can train on Seneca/Duchess/Cessna and be stuck with 1940s technology but look how many DA42s are coming into the country - before long they will be as numerous at FTOs as the Seneca.
One or two questions - what do you plan to do with your CPL, ME Class Rating and MEIR? Do you plan to spend your career flying light twins or is it a step up to turboprops or jets? If it's the latter, then the DA42 is the most logical choice but if itīs the former, then find yourself an FTO with Senecas.