I am currently teaching 2 new people to add to my play group, and they are catching on pretty well. I first introduced them to a deck full of vanilla creatures, to get them to understand each steps, phases and combat. Then I slowly introduced other things. They don't really find the old rules confusing. Every new player will have to learn the rules no matter what, nothing will change that.

Based on the random casual scenes I've played, I could just imagine them doing a tweak on a few things, that I could already imagine. As those randoms I've played were somehow confused on a few things.

1) Doing things on my 2nd main phase. It seems like right after I attacked, newer players tend to think that your turn is over as there's nothing else you could do (in their opinion). Sometimes they tend to get a bit overboard and draw in to their card when I finished my attack but not saying "I end my turn".

2) Loss of Life vs Damage. Some thinks and do not understand why they couldn't use Circle of Protection: Black versus cards that would cause them to lose life. I could imagine this being tweaked in the future >_>