I play hamlet, tournament, had a wharf in play. I now play 3 coppers, a silver, a gold, and a Dividends. I now have $16, $7 of which from my Dividends.
If that was a Bank instead of a dividends, the value goes down by $1.
If it was a Horn of Plenty instead of a Dividends, it would gain me a card costing $7.
The potential to gain very high amounts are certainly there with Dividends, but it doesn't seem too much stronger than (or different than for that matter) existing treasures. Potion cost cards, Colony games, Peddler, Durations, and Shelters ($1 Necropolis) add to the potential craziness. It seems good to me.