It was so much that a good chunk of us (including myself) flirted with starting somebody else. Zach made a lot on mental errors in previous seasons instead of just running the offense and letting the game come to him. Lesser talented QB (like Romney) looked better at times simply because they played conservative, mistake free football.
Then Zach took it to another level. His passing improved even more (health was a huge issue) and his decision making greatly improved. Combine the two and we saw a generational talent at BYU.