Great idea & helpful, but . . .
This app is a great idea and very helpful when playing 500, but it can use some touch ups.
The major improvement I would like to see is the addition of 6 bids. The version of the game I play allows for 6 bids, but the scorer in its current version is unusable for us. Adding the option in the scorer for 6 bids would not hinder those who don't play with 6 bids but it would make it versatile for those of us who do.
Also, the look could be upgraded a bit to be made more rich and inviting (maybe give it a card table motif?), and some extras should be added, like rules of play, trump suit ranking, and other tips.
The suggestions offered in the other reviews here are also good, keeping track of the dealer is a good one, add the "score chart" to see bid values and the error checking are very good ideas. The extra 50 points for taking all 10 tricks is not a good idea, however, since the app already awards -- correctly -- 250 points if all 10 tricks are taken on a bid that is valued at less than 250. There is no additional reward for taking 10 tricks allowed in the rules.