I only played one head to head game in the demo so far. I do think its a definite improvement.
The running and foot-planting is a huge improvement. The run game seems like it could be a bit overpowered but I think there may be fewer huge runs because of the improved stamina system. It seemed like if I had to make a couple moves or hammer on the speed burst to get into the open I would usually get caught before the endzone. But the 20 yard runs were a lot more frequent than in the past so rushing averages will most likely still be extremely high.
Passing game still seems to have the same flaws on the same routes. And the pass rush is pretty weak. Actually the game feels very similar to NCAA 14 but for whatever reason the NCAA pass rush is much better which in turn makes passing more difficult/realistic in NCAA too.
Also, in my only game I got the invisible player bug too. They say it will be fixed in a day 1 patch though.
I will play it some more when I get home this weekend but my initial impression is to just wait for the PS4 version and hope these problems that have plagued the series for years will be solved in the next-gen version of M25.