When Apple announced its new free-plus-paid model last week, ngmoco was lightning quick off the mark with a free version of Rolando 2 that was loaded up with in-app purchases if you wanted to unlock the game's chapters piecemeal.

As I suggested back then, plenty of developers would be tracking the progress of the app to see whether it proved if this new business model worked.

We can't yet go that far, but we can say Rolando 2 is storming up the US free App Store chart.

Over the past 24 hours, it's jumped 60 places and is about to enter the top 40.

Of course, what would be really significant would be to find out how much revenue ngmoco is generating from the previously priced $4.99, €3.99, $2.99 game in terms of users unlocking new chapters at 99c a pop.

However, it doesn't seem that Apple is yet including such micro-transactions within the Top Grossing chart, or if it is, Rolando 2 isn't yet generating a lot of gross.