I'm personally very happy to see the upgrade!
It actually motivated me to buy some diamonds - got a bit unlucky in one of my cities, and no I would hot have bought them if they where a hard "wall" to get stuff - because in my other city I got level 10 with over 2k drinks to spare.
As for people complaining that they did not know - well that's part of the game, isn't it? If you can be patient and hold out there is a chance that something better is coming, if you want a smaller but more certain reward you grab it right away. I did not know if the upgrade would be available just like anyone else, but I hoped for it and it worked out
Good job Inno and thank you for adding it do daily specials
Now I can say this is probably one of the best events you made so far - the quests are great, the rewards balanced and I'm happy