If you really need huge number of micropaiements per client per day, I'd suggest you to use a different paiement system.

You could use an account-based paiement system.  Optionnaly this could use David Chaum's e-cash system if you want anonymity.

Anyway, your clients would have an account on your server, and they could change their balance into bitcoin when it reaches a significtive amount, or on a daily basis.