Practice Tool has been a huge success.
Granted, there's a few things I've made note of that could improve it. However, as a whole, I think it's been a huge success.
I say this for one core reason - mechanics that used to be primarily accessible to high elo players/one-tricks/high elo one-tricks are accessible to the average player. I learned the Alistar W Q Flash combo in about 5 minutes in a practice tool game, same with J4 E Q Flash, same with Camille E Flash, and on and on.
Things I rarely even saw on pro streams I can commit to learning and pull off consistently in my own games.