Really fun! For the sake of time, I limited myself to 4 quarters unlike the 12 quarters in a standard football game ;) It felt a bit easy with the upgrades staying a consistent price - having the upgrade cost go up a bit each time might add a little extra challenge.
edit: Apparently I left this running in the background so I managed to catch the last down on the 12th quarter and watch it roll over to 1st quarter, 1st down and keep going ;)