Last month we announced the removal of our global API limit, which was hampering the growth of some of our larger apps. Today I have some more good news: The per-shop limit has been raised from 300 calls every 10 minutes to 500 calls every 5 minutes. This works out to a 3(-and-a-bit)-fold increase over the previous number, and should accommodate the vast majority of apps.
The best part about this announcement is that the change has already been rolled out, and you should see the new numbers appearing in the HTTP_X_SHOPIFY_SHOP_API_CALL_LIMIT header in our API responses.
We're in the process of updating our docs to reflect this change, but if you see any references to the old numbers on the wiki feel free to swap them out for the new ones or just ping me about it if you're lazy :)