I was surprised to see in-app sales were only for paid apps. I imagine a big market where apps "hook" a user by being free, then make money from in-app sales.
A lot of developers may try to abuse this by creating tons of free apps with paid content. Then it will be impossible to know whether the apps your downloading are really free.
But I still think there's value in a free app that has paid upgrades, even if Apple has to classify them as "Mixed" instead of Free or Paid.
In fact for paid apps its even worse because the developer has already gotten the $4.99 from me(which used to be their sole source of revenue up to this point), so any additional money I'd pay would just be bonus, so they have no incentives not to abuse the nickel and dime option