CAVOK - thanks for kicking off an interesting thread.
I just want to say that I converted to the (not very complex) Dakota within I think 10 hrs or so of getting PPL and wouldn't say it was particularly difficult. In fact, I'd say its great - go fo it! There's a few things to know about proper operation and emegency handling of Prop/MP, but not hard.
Main difference in flying it, as others have said, is getting used to the greater speed initially, e.g. remembering to slow-down before entering the circuit!
Together with my good friend "1013.25" I've done a few enjoyable trips in "the Dak" - I love it! In fact, looking forward to planned trip to Barcelona in it in May
Andy