I wonder how feasible it is to do batch payments for Bitcoin or even credit card. Apple seems to do this successfully with its iTunes store (a typical micropayment use case) by charging credit cards in batches of $20 to $50 over a certain period.

If there's a payment aggregator doing this for a number of micropayment merchants, I can see some future in this. However, Bitcoin protocol is not compatible with polling transactions retrospectively, so that requires either a "credit" account or a small deposit to start with.