Over on Twitter, he says that the 99 cent charges are the most common, making up half of the total purchases. But the $29.99 optional charges make up 8% of the purchases, and actually contribute to 49% of total revenue. In other words, just a few people are responsible for half of the game's total revenue -- the freemium model hard at work.
Marsh says that NimbleBit is working on updating the game, too. They don't plan to increase the size of the in-game frog "catalog," since the whole point of the game is to have the player make decisions about which frogs to keep and breed, but they are working on something tentatively called the "Frogodex," which would passively track every frog ever collected by players in the game. They're also considering integrating Game Center in terms of leaderboards and achievements in the future -- they originally decided to go with Ngmoco's Plus+ system because it "provides a number of services crucial to social game developers which Game Center does not," including backing up game data and doing things like browsing your friends' frog habitats.
And finally, Marsh says the company has been overwhelmed by all of the positive feedback, and the feature request list "is growing faster every day." The next big update they're planning, he tells TUAW, will be "a rare new pattern color mutation" that he thinks people will like. And he also tells us to look out for "exclusive surprises in-store for upcoming holidays." Sounds like NimbleBit has a nice freemium hit on their hands, and we'll look forward to updates in the future.