Couldn't agree with you more, mate! In the recordings with the original speed, Robert Johnson sounds more like a bluesman and more importantly, sounds HUMAN!
You know, when I first heard the incorrect version of "Preaching Blues", I honestly thought that I was listening to an alien man singing and playing the guitar and it did creep me out a bit!
Apparently, the aim of increasing the speed of these 78's, was to make these recordings sound more "exciting"! And some people on YT actually think that the recordings with the corrected speed, sound simply awful and are severely scolding all those poor souls who are taking the initiative to make sure that we all get to hear the great bluesman, as he was meant to be heard! Sheesh!
http://youtu.be/MykGQ4SnWnM
Also, with the correct speed, I find it a lot easier to understand what the guy is actually singing about!
I really appreciated this YT user's efforts in bringing the REAL Robert Johnson, to all of us Blues fans: https://www.youtube.com/user/zimmyfan115/